Set this problem as a 2 × 2 linear system and solve it.

Question

A boy has a stamp collection consisting of 5-cent stamps and 8-cent stamps. His collection has a total of 48 stamps worth $3.48. How many of each kind of stamp does he have in his collection?

Answer 1

Let x be the # of 5-cent stamps and y be the # of 8-cent stamps.

0.05x + 0.08y = 3.48

x + y = 48

Multiply the top equation by 20 and the bottom equation by -1.

x + 1.6y = 69.6

-x - y = -48

Eliminate the x's so we can focus on y.

0.6y = 21.6

y = 36

x + 36 = 48

x = 12

A boy will collect 12 five-cent stamps and 36 eight-cent stamps.