first you move the 15 to the 13 side like this:
16x-9x=13+15
If you move it, the sign always changes.
Then you do calculations.
16x-9x=(16-9)*x=7x
13+15=28
That means:
7x=28
Now you divide 7 from both sides:
x=4
So neatly, this is what it looks like:
16x-9x=13+15
7x=28
x=28/7
x=9
-Isb
