Let d and q be the number of dimes and quarters respectively.
10 cents* d+ 25 cents* q = 620 cents ($6.20 = 620 cents)
⇒ 10d + 25q = 620 (1)
On the other hand, we have: d+ q= 32 (coins) (2)
From (1) and (2), we solve the set of equations.
The final answer is d= 12 coins and q= 20 coins.