Achild’s piggy bank contains quarters and dollar coins. there are 6 times as many quarters as dollar coins. if there are 140 coins the piggy bank, what is the total amount of money it contains?

120 Quarters, 20 Dollar coins = $50

Variables well use:
Quarters = Q
Dollar Coins = D

What we know:
Q + D = 140
Q = 6(D)

First well substitute Q into the first equation to find the amount of dollar coins (D). 
6D+D = 140
7D = 140
D = 20

Since we know how many dollar coins are in the piggy bank and also how many coins total, we can substract the total amount of coins minus the amount of dollar coins to find the amount of quarters.

140 - 20 = 120 Q

To find the total money amount we take the variables we solved for and multiply is by the money amount:

(120(.25)) + (20(1)) = $50