Question 201379
Let x=number of quarters
Then 4x =number of dimes
And y=number of nickels
Now we are told that:

x+4x+y=25 or
5x+y=25--------------------eq1
also (we'll deal in pennies)
25x+10*4x+5y=205
65x+5y=205-------------------------eq2
multiply eq1 by 5 and then subtract it from eq2
(65x+5y=205)-(25x+5y=125) and we get
40x=80
x=2---------------number of quarters
4x=4*2=8 number of dimes
There must be 25-10=15 nickels

CK
2*25+8*10+15*5=205
50+80+75=205
205=205

We can also work this problem using only one unknown:
Let x=number of quarters
Then 4x =number of dimes
And 25-5x=number of nickels
So we have:
25x+10*4x+5(25-5x)=205 get rid of parens
25x+40x+125-25x=205  subtract 125 from each side
25x+40x+125-125-25x=205-125  collect like terms
40x=80---same as before

Hope this helps---ptaylor