Question

(3a) You spend $72 on tapes and CDs. Each tape costs $8 and each CD costs $12.

(3b) You buy a total of 7 tapes and CDs.

How can I set it up

Answer 1

3a. 8t + 12c = 72

3b. t + c = 7

Explanation:

number of tapes is t

number of Cds is c

so 8t + 12c = 72

and t + c = 7

so t = 7 - c

replace t = 7 - c in to the first equation

8(7 - c) + 12c = 72

56 - 8c + 12c = 72

4c = 72 - 56 = 16

c = 4

if c = 4, then t = 7 - c = 7 - 4 = 3