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.