Question 59411
Let x be the number of nickels the clerk returned.
So number of dimes brought = x + 9
Number of quarters retuned = (x+9) + 21
                           = x + 30

Value of x nickels = 5x cents
Value of (x + 9) dimes = 10(x+9)
                       = 10x + 90 cents


Value of (x + 30) quarters = 25(x + 30)
                       = 25x + 750 cents
Total value = 1000cents

==> 5x + 10x + 90 + 25x + 750 = 1000
==> 40x + 840 = 1000
==> 40x = 160 [subtracting 840 from both the sides]
==> x = 4 [dividing by 40 on both the sides]

Number of nickels = 4
Number of dimes = 4 + 9 = 13
Number of quarters = 4 + 30 = 34