Hi there!
First, let's find the period of the pendulum. This can be found by solving for the amount of time it takes for the pendulum to make ONE complete swing.
Now, let's use the equation for the period of a simple pendulum:
T = Period (1.318 s)
L = length of string (0.55 m)
g = acceleration due to gravity on planet (? m/s²)
Let's solve for 'g' doing some quick rearranging of the equation:
Solving for 'g' by plugging in values: