Question 1033221
1.{{{M+N=13}}}
2.{{{N=1+3*M}}}
Substituting eq. 2 into eq. 1,
{{{M+(1+3*M)=13}}}
{{{4M+1=13}}}
{{{4M=12}}}
{{{M=3}}}
Now use either equation to solve for N.