So we know that John has 8 less nickels than dimes.
10¢= one dime
5¢= on nickel
8x5=40
Multiply 8 with 5 first because you know John hase 8 less nickels than dimes.
Subtract $8.30 with 40¢. Answer: $7.90. $7.90 divide 10 is 79 so then the left over is 0.
Final result: 79 dimes and 8 nickels.