Everywhere you see x in the equation replace it with 1 like so...
3(1) + y = 5
3 + y = 5
Finish isolating y. To do this first subtract 3 to both sides (what you do on one side you must do to the other). Since 3 is being added, subtraction (the opposite of addition) will cancel 3 out (make it zero) from the left side and bring it over to the right side.
3 - 3 + y = 5 - 3
0 + y = 2
When x is 1 then y is 2
Check:
3(1) + 2 = 5
3 + 2 = 5
5 = 5
Hope this helped!
~Just a girl in love with Shawn Mendes