Math
posted by curtis .
the banks contains quarters , dime and nickels. The number of dimes is 1 less than the number of nickels. The number of nickels is 2 more than twice the number of quarters. The coins are worth $5.70. How many nickels are there?

Just take each sentence and write it symbols.
d = n1
n = 2 + 2q
10d + 5n + 25q = 570
substitute for d:
10(n1) + 5n + 25q = 570
10n  10 + 5n + 25q = 570
15n + 25q = 580
substitute for n:
15(2+2q) + 25q = 580
30 + 30q + 25q = 580
55q = 550
q = 10
so, n = 2+2*10 = 22
so, d = 221 = 21
10(21) + 5(22) + 10(25) = 210 + 110 + 250 = 5.70