In science, rate is a quantity measured with respect to another measured quantity. For the data given, we get the rate of each by calculating the slope. We do as follows:
Megan's rate = 12 - 4.5 / 4 -1 = 2.5 inches per week
Suzanne's rate = 11 - 5 / 4-1 = 0.5 inches per week
Therefore, the plant that grew at a faster rate would be Megan’s at 2.5 inches per week.