Sofia can type the work in 10 hours. Noga can do it in 15 hours. They work together for 4 hours. Then Sofia left and Noga finished the job. How long did it take to do the entire job?

You subtract from sofia four hours from 10 and subtract from noga 4 hours so they said that noga did the rest of the job so you add 8+11=19 hours

So they did the entire job for 19 hours