Jenna's age Jessica's age
today x x + 5
in 5 years x+5
5 years ago x + 5 - 5
Equality x + 5 = x + 5 - 5
=> x + 5 = x
The equation is x + 5 = x
That equation has not any solution, because it reduces to 5 = 0, which is an absurd.
So, the conclusion is that information given by Jenna is wrong.
It is logical: if the difference of the ages is 5, in five years Jenna will have 10 years more than what her sister had 5 years ago, no 5 as she told Jessica.