Use Algebra
John has 18 coins in dimes and quarters. Their total value is $3.45. How many coins are there of each type?
d=dimes
q=quartes
d+q=18
.10d + .25q=3.45
d=18-q sub
.10(18-q)+.25q=3.45
1.8-.10q+.25q=3.45
.15q=3.45-1.8
.15q=1.65
q=11 quarters
d=7 dimes.
