Question 120966
Solve the first equation for y:
{{{y=(5/2)x+5/2}}}
Substitute this into the second equation for y:

{{{(5/2)x+5/2-5x=3}}}
Solve:
{{{(-5/2)x=1/2}}}
{{{x=-1/5}}}

Substitute this x into the first equation we found:
{{{y=(5/2)(-1/5)+5/2=-1/2+5/2=2}}}

Which gives solution set S={(-1/5,2)}

I will leave the check up to you.

In sum:
1) Solve one of the equations for a variable, generally y.
2) Plug the y gotten in step 1 into the other equation.
3) Solve for the other variable in this new equation (generally x).
4) Plug the value of x into the equation gotten in step 1 for the value of y.
5. Check