Question

A corner store sells two kinds of baked goods: cakes and pies. A cake costs $5 and a pie costs $7. In one day, the store sold 15 baked goods for a total of $91. How many cakes did they sell?

Answer 1

Let the quantity of cakes sold = C
Let the quantity of pies sold = P
5C + 7P = 91
C + P = 15
Multiply both sides of C + P = 15 by 7 to give:
7C + 7P = 105
Subtract 5C + 7P = 91 from the last equation to get:
2C = 14
C = 7 = quantity of cakes sold