This is a problem of guess and check; there's no easier way to do it.But in this case you must have an odd number of nickels to make the 5 cents, so your answer is 9 nickels.you can check this by multiplying each one by .05:
9.05=.45
the rest of the coins left, are 8 of them, and their dimes.
.108=.80
.80+.45= 1.25
