Question 1103161
1.{{{N+D=50}}}
.
.
.
{{{5N+10D=455}}}
2.{{{N+2D=91}}}
Subtract eq. 1 from eq. 2,
{{{N+2D-N-D=91-50}}}
{{{D=91-50}}}
Solve for D then use either equation to solve for N.