The number of quarters . . . . . Q
The value of the quarters . . . 25 Q cents
The number of dimes . . . . . . . 2 Q
The value of the dimes . . . . . . 10 (2Q) = 20 Q cents
The total value of all the coins . . . 25Q + 20Q
= 45Q cents = 4185 cents
Divide each side by 45 cents : Q = 93
2 Q = 186
Benny has 93 quarters and 186 dimes.
Check:
93 quarters are worth (0.25) x (93) = $23.25
186 dimes are worth (0.10) x (186) = $18.60
Total value of all the coins: ($23.25) + ($18.60) = $41.85 yay !