Let the number of pennies be p, quarters be q and dimes be d. The value of pennies is 0.01, the vale of quarters is 0.25 and the value of dimes is 0.10
As per the given question
p+q+d = 63 ............. (1)
0.01p + 0.25q + 0.10d = 6.30 ........... (2)
d = q-3................ (3)
Put the value of d from eq. 3 to eq. 1 and 2
p+q+q-3 = 63
p+2q=66 .......... (4)
0.01p + 0.25q +0.10(q-3) = 6.30
0.01p+0.25q+0.10q-0.30=6.30
0.01p+0.35q=6.6
p+35q=660......... (5)
Solving (4) and (5)
35q-2q=594
33q=594
q=594/33=54/3=18
And d = q-3=15
p=66-2q=66-36=30
Therefore number of pennies=30
Number of quarters = 18 and number of dimes = 15