Y=2x+3 x+2y=2 solve by substitution .

First you need to substitute Y (which equals 2x + 3) into the second equation.
X + 2(2X + 3) = 2     
Solve the parenthesis by the distributive property: X + 4X + 6 = 2
Add the x's: 5X + 6 = 2
Subtract 6 from both sides: 5X = -4 
Divide 5 from both sides: X=-4/5
Then, plug x into the first equation. 
Y=2(-4/5) + 3
Y= -8/5 + 3
Y= 7/5 

Then you can check your equations like this: 7/5 = 2(-4/5) + 3
7/5 = -8/5 + 3
7/5=7/5