
Nathan B. answered 03/09/15
Tutor
5
(20)
Elementary and Algebraic skilled
Let's start by defining our variables:
p = popcorn
d = drinks
Here's what we know:
2p + 4d = 22
3p + 2d = 21
I look at that 2d and 4d and see an easy elimination. By multiplying the second equation by -2, we can eliminate the d and solve for p:
2p + 4d = 22
-6p - 4d = -42
-6p - 4d = -42
-4p = -20
Divide both sides by -4, and:
p = 5
So popcorn costs $5. Using that, we can solve for d:
2 * 5 + 4d = 22
10 + 4d = 22
4d = 12
d = 3
So small drinks are $3.
Let's check our answer by putting the values into the second problem:
3 * 5 + 2 * 3 = 21
15 + 6 = 21
21 = 21