Answer:
3a. 8t + 12c = 72
3b. t + c = 7
Step-by-step 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
