Week 1 she lost 3 pounds
week 2 she gained 1 pound
so in the first 2 weeks she lost 3-1 = 2 pounds total.
13 weeks - 2 weeks = 11 weeks left.
Each of those weeks she lost 2 pounds, so 11 weeks x 2 pounds = 22 total pounds in 11 weeks.
22 pounds +2 pounds = 24 total pounds lost in 13 weeks.
The answer is D.