Answer:
Quarters: 7
Dimes: 9
Nickels: 14
Step-by-step explanation:
Bank --> 30 coins
Base Equations:
N+D+Q=30
5N+10D+25Q=335
Equation 1: 2Q=N
Equation 2: D=30-(N+Q)
          Substitute Equation1 :  D=30-(2Q+Q)
          D=30-3Q
0.05(2Q)+0.10(30-3Q)+0.25Q=3.35
0.10Q+3-0.3Q+0.25Q=3.35
0.5Q+3=3.35
0.5Q=0.35
Q=7
if Q=7, N= 2*Q
N=14
D=9
Check Step:
7*25=175
14*5=70
9*10=90
175+70+90=335
Correct