Volume follows vt+1 = 1.5vt, with v0 = 1220m3. Compose the updating function associated with each discrete-time

Question:

Volume follows vt+1 = 1.5vt, with v0 = 1220μm3.
Compose the updating function associated with each discrete-time dynamical system with itself. Find the two-step discrete-time dynamical system. Check that the result of applying the original discrete-time dynamical system twice to the given initial condition matches the result of applying the new discrete-time dynamical system to the given initial condition once.