Ian has 100 / 2 = 50 dollars. Rodney has 50 + 35 = 85 dollars. Jessica has 100 - 85 = 15 more dollars than Rodney.
This justifies what answer for what question? Q & A:
Rodney has 35 dollars more than Ian. Ian has half as much money as Jessica has. If Jessica has 100 dollars, how much more money does Jessica have than Rodney?
15