Question

Anna and Belle are asked to solve −2x − 15 = 6x + 9. Identify where one of them made an error.

Answer 1

Ok so first you need to identify what you are looking for... you need to find x. 
to do that you need toge it on one side. so cancel out the "-2x" on the left side by adding 2x(on both sides, don't forget you add common variables). now you should have something like this...
-15=8x+9
now all you have to do is get rid of the 9  by subtracting 9 on both sides
you should have 
-24=8x
 With that, all you have to do now is divide 8 into both sides and it should look like a fraction now

-24/8=8x/8
the 8x/8 will cancel out the 8 and you will have 
-24/8=x
Simplify that and you should get
-3=x
need me to explain it with fewer words?