I think you're saying that the exponent is (5x), and the equation is
6⁵ˣ = 20 .
IF so, then . . .
Take the log of each side: 5x·log(6) = log(20)
Divide each side by log(6) : 5x = log(20) / log(6)
Divide each side by 5 : x = 0.2 log(20) / log(6)
x = 0.2 · (1.30103) / (0.77815)
x = 0.33439
