angel can type a research paper in 3 hours, ezra can do it in 4 hours and mira in 6 hours. How long will it take them to finish the job if they work together?

Solution:

Time needed working together: x

So the equation is

1/3 + 1/4 + 1/6 = 1/x

So

x = 4/3

So Time needed working together is 4/3 hours