Question

A jar contains $14.25 in quarters and dimes. There are 75 coins in the jar. Find the number of quarters in the jar.

Answer 1

Set up a system of equations.
d + q = 75
.1d + .25q = 14.25

Multiply the first equation by -.1 so that the "d's" will cancel.
-.1d -.1q = -7.5
.1d +.25q = 14.25
Now add the two equations together
      .15q = 6.75
divide both sides by .15
        q = 45
There are 45 quarters in the jar