Log2 + log (4x-1) = 3

Remember

logx+logy=log (xy) so

log2+log (4x-1) = log2 (4x-1) = log8x-1

since no base is mentioned, it it base 10

now we have

log 8x-2, base 10=3

means

10 must be raised to the 3rd power to get 8x-2

therfor

10^3=8x-2

1000=8x-2

1002=8x

divide 8 both sides

125.25=x

x=125.25

10^2.7=4x-1

(10^2.7+1) / 4=x

x=125.55