Chase can do a job in 3 hours, whereas Campbell takes 4 hours to do the same job. If they work together, how long would it take them to finish the job?
These types of problems aren't too bad
Each hour, Chase does 1/3 of the job and Campbell does 1/4 of the job
Add these fractions
1/3 + 1/4 = 7/12
Take the reciprocal = 12 / 7 hrs = time for both working together to do the job