Question 12023
Let number of nickels be "x".
Then number of dimes is "2x".
And number of quarters is "30-3x"
Value of nickels is (5)x cents
Value dimes is (10)2x = 20x cents
Value of quarters is (25)(30-3x)= 750-75x cents
EQUATION:
Value of nickels + Value of dimes + Value of quarters = 550 cents
 5x + 20x + 750-75x = 550
            -50 x = -200
                x = 4 (number of nickels)
               2x = 8 (number of dimes)
          30-3x = 30-12 = 18 (number of quarters)

Cheers,
Stan H.