Answer:
11 pennies
33 nickels
7 quarters
Explanation:
Let x be the number of pennies, then the number of nickels is 3x.
There are 51 coins in total, so the number of quarters is 51 - x - 3x = 51 - 4x.
Amounts:
- in pennis - x cents;
- in nickels - 5(3x) = 15x cents;
- in quarters - 25(51 - 4x) cents.
Tota amount = $3.51 = 351 cents.
Hence,

11 pennies
33 nickels
7 quarters