What is the solution of log2x − 4 16 = 4?
x = −3
x = 3
x = −2
x = 2

Using the property of logarithms log(a)b = x => a^x = b so we get 

(2x-4)^4 = 16 

(2x-4)^4 = 2^4    because the exponents are equal so this equation will be right than the bases will be equals too so than 

2x -4 = 2

2x = 6

x = 6/2 = 3 

x = 3 

hope this will help you 

The answer to that is 6