Answer:
So if Jill, Sabrina and Kelly write the report together, it will take 4 hours.
Step-by-step explanation:
We know that Jill and Sabrina can write a lab report together in 6 hours. We know that all people work at the same rate.
So, we conclude that it will take Jill or Sabrina 12 hours if they write the report themselves. Kelly will also need 12 hours to write a report because we know everyone is working at the same speed.
We conclude that if all three work together they will need three times less time. We get:
So if Jill, Sabrina and Kelly write the report together, it will take 4 hours.