.
Let N be the number of nickels and Q be the number of quarters.
Then the number of dimes is 2N.
Nickels contribute 5N cents to the total.
Dimes contribute 10*(2N) = 20N cents to the total.
Quarter contribute 25Q cents.
Hence, the "value" equation is
5N + 20N + 25Q = 650 cents, or
25N + 25Q = 650, or
N + Q = 26,
The "coins" equation is
N + 2N + 5Q = 58, or
3N + 5Q = 58.
So, you have this system
N + Q = 26, (1)
3N + 5Q = 58. (2)
The setup is done.
Solve the system by any method you know (substitution, elimination).