Hi Mella,
So we basically have:
⇒ x = 7 + y
In order to write this in terms of y, then basically we just have to solve for y. To do this, let's look at the equation again to see how we can get y by itself.
⇒ x = y + 7
If we subtract 7 from both sides, we now have
⇒ x - 7 = y which is the same as y = x - 7.
x is now expressed as a function of y.
-Hope this helps!
