Since we alredy know that y = 6 we can go ahead and insert it into the problem. It would look like this:
x + 4 = 6
Now we can begin to solve.
Since positive 4 is on one side, we can subtract it from both sides
It will look like this:
x + 4 = 6
x - 4 = 6 - 4
You end up with
x = 2
Now substitute all your known variables.
It will look like
2 + 4 = 6
This equation is true.