math for boilogy ? please help me with the solution ? :))?

) in a fetus, the number of neuronal synapses in the brain follows the discrete-time dynamical system s(t+1) = 1.8s(t) ; s(0) = 1*10^3 where t is in weeks. How long will it take for the fetus's synopse number to reach the level s(t) = 1 *10^10?