The eqn x-3y=7 can be written x=3y+7 and then this value of x substituted in the other eqn: 4(3y+7)+y=5 giving an eqn with just one variable. This can be solved: 12y+28+y=5, 13y+28=5 and 13y=5-28=-23, making y=-23/13. We now substitute y in x=3y+7 giving x=-69/13+7=(91-69)/13=22/13. To check the answer, plug these values into the original eqns: 22/13-(-69/13)=91/13=7; 88/13-23/13=65/13=5.