Log4 8= simplify using properties of logarithm 

8 = (2) cubed.So log(8) in any base = 3 log(2) in the same base.But 2 is the square root of 4, so in the base of 4, log₄(2) = 1/2log₄(8) = 3 log₄(2) = 3 x 1/2 = 1.5

using logarithm property,log4(8) = log10(8) / log10(4)= log10(2)^3 / log10(2)^2= 3*log10(2) / 2*log10(2)= 3/2= 1.5