Two welders working together can complete a job in 6 h. one of the welders, working alone, can complete the task in 15 h. how long would it take the second welder, working alone, to complete the task?

Ur asking a bunch of these kind of rate problems xD

In 6 hrs, the welder who does 1/15 of the job in 1 hr and the welder who does 1/x in 1 hr, complete the job (6 hrs.)

Multiply 30 on both sides to cancel out the fractions and we get:

Solving for x:
30/x=3
3x=30
x=10
The second welder would take 10 hours.