5x+15=3x+27

could someone explain the method of working out x?

Sure! So first..when you're solving you want all the X's to be on the left side of the problem and you want a number on the right for example like this 2x=4. So first you want to minus the 3x to the 5x because you're trying to get it to the left side(you can only + or - numbers with the same variable). And 5-3= 2. So now you have 2x+15=27. But like I said you want all numbers without the x variable to go to the right so you do 27-15= 12. So now you have 2x=12. And now to fully solve x you're gonna divide the 2 and the twelve. So your answer is x=6!

If you move the 3x to the other side you would get:

5x+15=3x+27
-3x      -3x

2x+15=27

Then if you move the 15 to the other side

2x+15=27
     -15 -15

2x=12

Then divide 12 by 2

2x=12
---   ---
 2     2

x=6

And x=6!