The abscissa is the x-coordinate of a point (x,y).
The ordinate is the y-coordinate of a point (x,y).

The way to remember which is which is that "x" comes 
before "y" in the alphabet, and "a" for (abscissa)
comes before "o" (for ordinate) in the alphabet.

That says:

x is two less than y

To get "two less than y" we must subtract 2 from y:

x = y - 2

We solve that for y:

Swap sides

y - 2 = x

Add 2 to both sides:

    y = x + 2

Edwin