Let x be the number of quarters. Let 6x be the number of dimes

Since one quarter equals 25 cents, x quarters equals x × 25 cents or 25x cents

Since one dime equals 10 cents, 6x dimes equals 6x × 10 cents or 60x cents

Since one 1 dollar equals 100 cents, 2.55 dollars equals 2.55 × 100 = 255 cents

Putting it all together, 25x cents + 60x cents = 255 cents

85x cents = 255 cents

85x cents / 85 cents = 255 cents / 85 cents