When you have a system of equations the first thing you want to do is find a value for one variable. So the first equation x+3y=7 we are going to rewrite so we get a value for x; X=-3y+7
Now with second equation 3x+2y=O we will rewrite “substituting” x for the value we found :
3(-3y+7)+2y=0
Now do distributive property
-9y+7+2y=0
Combine like terms
-7y+7=0
Subtract seven on both sides
-7y=-7
Divide both sides by -7
y =1
Now we have to find the value of X so plug in 1 for y in the first original problem
x + 3(1) =7
x +3=7
Subtract three from both sides
x =4
So final answer x =4; y =1