Hi there!
The period is given by:

T = Period (sec)
w = angular frequency (rad/sec)
According to the equation for SHM in terms of position:
y(t) = Asin(ωt + φ)
A = Amplitude (m)
ω = angular frequency (rad/sec)
t = time (sec)
φ = phase angle
In this instance, the angular frequency is given as 18π.
Plug this value into the equation for T:
