Exponential function

Question

I got stuck while solving this question. Didn't know how else to proceed. Please could you help?

A quantity N is decreasing such that at time t, N = N_oe^-bt, where N_o is the amount at t = 0 and b = 0.5. Find the value of t when N = N_o/5.

Answer 1

N = N₀e^-bt

0.2N₀ = N₀e^-0.5t

0.2 = e^-0.5t

ln 0.2 = -0.5t

Can you solve for t and answer?