So, you need 10 penny, 4 nickles and 7 dimes
Lets, check it.
According to the question,
total coins = 21
7 + 4 + 10 = 21
21 = 21.........................................true
Now,
their value should equal $1.00 = 100 cents
Penny = 1 cent
nickle = 5 cent
dime = 10 cent,
So,
(10 *1) + (4 * 5) + (7 * 10) = 100
10 + 20 + 70 = 100
100 = 100......................................true
So, you need 10 penny, 4 nickle, and 7 dimes