First of all, add 7 to both sides, in order to cancel the -7:

As we said, the -7 on the left hand side cancels out, while we can add it to the 9 on the right hand side:

Now, divide both sides by 4. As before, this is needed to cancel the four on the left hand side and isolate the x, while it is just a normal division between numbers on the right:
