Problema Solution
Sydney's parents pay her according to her grades. For each "A" that she earns, they add $12 and for each "C" they subtract $5. On a recent grade period, she got only "A's" and "C's" for her 6 classes. If she got a total of $21, how many of each grade did she get?
Answer provided by our tutors
A + C = 6
12A - 5C = 21
A = 6 - C
12(6 - C) - 5C = 21
72 - 12C - 5C = 21
72 - 17C = 21
-17C = -51
C = 3
A = 6 - C
A = 6 - 3
A = 3
so she got 3 A's and 3 C's