Using the exponential growth formula A = P(1+r)^t
P is the starting value ( 11 square cm)
r is the rate ( 1.5 means a 50% growth, so rate would be 0.50)
t is the amount of time ( 6 months)
Now you have:
A = 11(1+0.5)^6
A = 11(1.5)^6
A = 125.3 cm^2
The answer is A.