a certain job can be done in 20 hours by 4 people. how many people are needed to do the same job in 10 hours?

If it takes 4 people to get a job done in 20 hours, then in 10 hours, it will take 2 people to complete the same job.
To find out how many people are needed to do this job in 10 hours, we can see that we got to 10 hours by dividing 20 by two so, to see how many people are needed to complete this same job in ten hours, we would just divide 4 people by 2 which is 2 people.
So, in conclusion, if it takes a certain job to be done in 20 hours by 4 people, then it would take 10 hours for that same job to be completed by 2 people.
Glad I could help!

Use photo math it