Question

quick copy recently charged 49 cents per page for color copies and 7 cent per page for black and white copies. if shirly's bill for 90 copies was 11.34 how many copies of eahc type were made.

Answer 1

c is color copies
b is black and white copies

49c + 7b = 1134
c + b = 90 ---> c = 90 - b

Now substitute 90 - b in for c in the first equation...
49c + 7b = 1134
49(90 - b) + 7b = 1134
4410 - 49b + 7b = 1134
-49b + 7b = 1134 - 4410
- 42b = - 3276
b = 3276/42
b = 78

Now substitute 78 in for b in the second equation...
c = 90 - b
c = 90 - 78
c = 12

check...remember c = 12 and b = 78
.49c + .07b = 11.34
.49(12) + .07(78) = 11.34
5.88 + 5.46 = 11.34
11.34 = 11.34 (correct)

ANSWER : Shirly bought 12 color copies at .49 cents each, totaling $ 5.88 and 78 black and white copies at .07 cents each, totaling $ 5.46. Total is 90 copies for $ 11.34.