add -2x to both sides to get 'x' on one side of the equation
-2x-3=4x-15
+2x +2x
__________
-3=6x-15
add 15 to both sides to isolate 6x
-3=6x-15
+15=6x+15
__________
12=6x
divide both sides by 6 to get 'x' alone
12=6x
/6=/6
_____
2=x
so your answer is 2=x or you can flip it and it will be the same, x=2