Question 1079077
1.{{{Q+N=21}}}
.
.
.
{{{25Q+5N=405}}}
2.{{{5Q+N=81}}}
Subtract eq. 1 from eq. 2,
{{{5Q+N-Q-N=81-21}}}
{{{4Q=60}}}
Solve for Q then use either equation to solve for N.