Answer:
Step-by-step explanation:
d + q = 99.....d = 99 - q
0.10d + 0.25q = 21
0.10(99 - q) + 0.25q = 21
9.9 - 0.10q + 0.25q = 21
-0.10q + 0.25q = 21 - 9.9
0.15q = 11.1
q = 11.1 / 0.15
q = 74 <===== he has 74 quarters
d = 99 - q
d = 99 - 74
d = 25 <=== he has 25 dimes
check...
0.10d + 0.25q = 21
0.10(25) + 0.25(74) = 21
2.50 + 18.50 = 21
21 = 21 (correct)
