when mary emptied her bank she found that she had 84 coins,all nickels and dimes. The value of the coins was $7.15. How many dimes did she have. can i see the process thanks

Question

radar · Answer

Let x =dimes
Let 84-x =nickels

radar · Answer

10x+5(84-x)=715
10x+420-5x=715
5x=295
x=59 dimes
84-59=25 nickels
proof 5.90+1.25=7.15
59+25=84 coins

radar · Answer

Is there any part you do not understand?

anonymous · Answer

why is X dimes and not the nickels

radar · Answer

an arbitrary choice on my part.  I could of just as easy chose x to represent the number of nickels.  Then 84-x would of been the dimes.  However the following equations would of been changed to represent the different values the revised equation would of been:  5x+10(84-x) = 715

radar · Answer

Comprehendo?

anonymous · Answer

i understand,
 thanks alot

radar · Answer

Great.  Remember you are in charge solving equations, but be consistent and logical.

anonymous · Answer

Yes i will remember