Answer:
Jennifer would complete the job on her own in 5 hours.
Step-by-step explanation:
Solving a quadratic equation:
Given a second order polynomial expressed by the following equation:
.
This polynomial has roots
such that
, given by the following formulas:



Rates
The together rate is the sum of their separates rate.
We have that:
Jennifer takes x hours to complete the job on her own, so her rate is 1/x.
Carl needs 15 hours longer than Jennifer, that is, 15 + x hours, so his rate is 1/(15+x).
The together rate is 1/4. So



Applying cross multiplication.



Quadratic equation with
. So



Since the time to complete the job has to be a positive value.
Jennifer would complete the job on her own in 5 hours.