Fehima has 4 times as many dimes as quarters.If her dimes and quarters have a value of $3.90, how many of each coin does she have?I want to know if my answer is correct.

Question

D=4(q)
0.10d+0.25q=3.90
0.10(4q)+0.25=3.90
0.40q+0.25q=3.90
65q=3.90
65
q=0.06
65q

Answer 1

d = 4 q

10 d + 25 q = 390

10 (4q) + 25 q = 390

65 q = 390

q = 6 etc

Your error is here:
0.40q+0.25q=3.90
then you said
65q=3.90
no
0.65 g = 3.90
3.90/0.65 = 6
not .06