Question 351463
Let {{{N}}} be the number of nickels, {{{Q}}} quarters.
1.{{{N+Q=13}}}
2.{{{5N+25Q=165}}}
Multiply eq. 1 by (-5) and add to eq. 2,
{{{-5N-5Q+5N+25Q=-65+165}}}
{{{20Q=100}}}
{{{highlight(Q=5)}}}
Then use either equation to solve for N.
{{{N+5=13}}}
{{{highlight(N=8)}}}
He has 8 nickels and 5 quarters.