standard_description: Use variables to represent quantities in a real-world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities.
problem_activity: Problem 1
Solve the system of linear equations using substitution. Describe how you can solve any system using substitution.
$${x+2y=8}$$
$${-3x+2y=16}$$
Problem 2
Solve the two systems below using substitution. Compare and contrast the two solutions. What do they each mean?
|          **           System A          **          |          **           System B          **          |
|-----------------------------------------------------|-----------------------------------------------------|
| $${y=2(-x+3)}$$                        $${2x+y=4}$$ | $${5x+20y=15}$$                        $${x+4y=3}$$ |


aligns: no