Question 1095529
he has twice as many dimes as nickels,
<pre><font size = 4><b>
Let N = number of nickels
Then 2N = the number of dimes.
</pre>
he has a total of 27 coins 
<pre>
        {{{matrix(1,9,

(matrix(3,1,Number,of,quarters)), 
"",
""="",
"",
27,
""-"",
(matrix(3,1,Number,of,nickels)),
""-"",
(matrix(3,1,Number,of,dimes)) )}}}
 
Number of quarters =  27 -    N    -    2N 
Number of quarters =  27 - 3N 

</pre>
Justin has $4.75 in quarters, dimes, and nickels
<pre>

{{{matrix(1,9,

(matrix(6,1,"$0.25",times,the,number,of,quarters)),
""+"",
(matrix(6,1,"$0.10",times,the,number,of,dimes)),
""+"",
(matrix(6,1,"$0.05",times,the,number,of,nickels)),
"",
""="",
"",
"$4.75"))}}}

   0.25N   +  0.10(2N) + 0.05(27-3N) =  4.75

Move the decimals two places right in each term:

     25N   +    10(2N) +    5(27-3N) =   475

Simplify and solve that for N, the number of nickels, 
then substitute what you get for N in:

2N = the number of dimes
27 - 3N = the number of quarters

Edwin</pre></b></font>