standard_description: Use numbers expressed in the form of a single digit times an integer power of 10 to estimate very large or very small quantities, and to express how many times as much one is than the other. For example, estimate the population of the United States as 3 × 108 and the population of the world as 7 × 109, and determine that the world population is more than 20 times larger.
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