step 1) work your way from the outside in on the left hand side staring with log base 2. Rewrite the equation in exponent form: log3(log4x) = 20
step 2) 20 = 1 so, log3(log4x) =1 then rewrite in exponent form again: 31 = log4(x)
step 3) 31 = 3 so, 3 = log4(x) then rewrite again in exponent form: 43=x, 4 cubed is 4*4*4=64 which would be your answer x=64