Apiggy bank contains $5.45 in dimes and quarters. if the bank contains 29 coins, how many quarters are in the bank?

12 quarters
17 quarters
21 quarters

There are 12 dimes in there
 and 17 quaters

.1x + .25y = 5.45
x + y = 29

Multiply the second equation by -.1
 .1x + .25y = 5.45
-.1x - .1y  = -2.9  Now add the equations together, the x's will cancel.

       .15y  = 2.55  Divide both sides by .15
         y = 17
29 - 17 = 12
12 dimes and 17 quarters

CHECK
12 * .1 + 17*.25 = $5.45