standard_description: Prove that, given a system of two equations in two variables, replacing one equation by the sum of that equation and a multiple of the other produces a system with the same solutions.
problem_activity: Problem 1
How many?
[IMG]
Problem 2
Determine the value of the unknown in each equation below.
a.
$$a = 7 \times 8$$
b.
$$42 \div b =7$$
c.
$$49 = 7 \times c$$
d.
$$d\div 7 = 9$$
Problem 3
Here is the partially filled-in multiplication table from Lessons 1 and 6.
| **           x          **  | **           1          ** | **           2          ** | **           3          ** | **           4          ** | **           5          ** | **           6          ** | **           7          ** | **           8          ** | **           9          ** | **           10          ** |
|-----------------------------|----------------------------|----------------------------|----------------------------|----------------------------|----------------------------|----------------------------|----------------------------|----------------------------|----------------------------|-----------------------------|
| **           1          **  |             1              |             2              |             3              |             4              |             5              |             6              |             7              |             8              |             9              |             10              |
| **           2          **  |             2              |             4              |             6              |             8              |             10             |             12             |             14             |             16             |             18             |             20              |
| **           3          **  |             3              |             6              |             9              |             12             |             15             |             18             |             21             |             24             |             27             |             30              |
| **           4          **  |             4              |             8              |             12             |             16             |             20             |             24             |             28             |             32             |             36             |             40              |
| **           5          **  |             5              |             10             |             15             |             20             |             25             |             30             |             35             |             40             |             45             |             50              |
| **           6          **  |             6              |             12             |             18             |             24             |             30             |             36             |             42             |             48             |             54             |             60              |
| **           7          **  |             7              |             14             |             21             |             28             |             35             |             42             |                            |                            |                            |             70              |
| **           8          **  |             8              |             16             |             24             |             32             |             40             |             48             |                            |                            |                            |             80              |
| **           9          **  |             9              |             18             |             27             |             36             |             45             |             54             |                            |                            |                            |             90              |
| **           10          ** |             10             |             20             |             30             |             40             |             50             |             60             |             70             |             80             |             90             |             100             |
Add the new facts you encountered in this lesson to your multiplication table.


aligns: no