Use the laws of exponents 
         and 
in reverse as
         and 

to rewrite the terms on the left of



as









Let u = 2x



Factor the left side:



u-8 = 0;   u+4 = 0
  u = 8;     u = -4

Since u = 2x

2x = 8;  2x = -4

The second has no real solution so we ignore it.
 
2x = 8

2x = 23

The bases are equal and positive and not 1, so 
the exponents are equal.

x = 3

Edwin