Question 1012361
A collection of nickels, dimes, and quarters consist of 16 coins 
<pre>
{{{N+D+Q=16}}}
</pre>
with a total of $1.55. 
<pre>
{{{"$0.05"N+"$0.10"D+"$0.25"Q="$1.55"}}}
</pre>
If the number of dimes is equal to the number of nickels, 
<pre>
{{{D = N}}}

So the system of equations is

{{{system(N+D+Q=16,"$0.05"N+"$0.10"D+"$0.25"Q="$1.55",D=N)}}}

Simplify the second equation by first taking away the dollar marks:

{{{system(N+D+Q=16,"0.05"N+"0.10"D+"0.25"Q="1.55",D=N)}}}

and then multiplying by 100

{{{system(N+D+Q=16,5N+10D+25Q=155,D=N)}}}

Substitute N for D in the first two equations:

{{{system(N+N+Q=16,5N+10N+25Q=155)}}}

Simplify

{{{system(2N+Q=16,15N+25Q=155)}}}

Now you can finish.

Edwin</pre>