Solve -- 23*2^3x=40

Answer 1

assuming you meant:
23*2^(3x) = 40
2^(3x) = 40/23

take log of both sides and use log rules
3x log2 = log40 - log23
x = (log40 - log23)/(3log2) = appr. ......

Answer 2

23*2^3x = 40.
2^3x = 40/23 = 1.739
3x*Log2 = Log1.739
3x = 0.7984
X = 0.26613.