The rate of eating gummies for Carly is:
In the graph we can see the rate of Jill, she started with 20 gummies, and after 30 minutes she had 16 gummies left. It means she ate 20-16=4 gummies in 30 minutes, thus the Jill's rate is:
If we compare both rates, in 15 minutes Carly ate 3 gummies and Jill ate 2 gummies, so, Carly is eating the gummies at a faster rate than Jill.