Im lost i dont know which one maybe a

An advertising firm has an old computer that can prepare a whole mailing in 6 hours. with the of newer model the job is complete in 2 hours. how long would it take the newer model to do the job alone?

The function v(r)=4/3pir^3 can be used to find the volume of air inside a basketball given its radius. what does v(r) represent

If the tip varies directly with the number of guest which equation represents between the tip,t, and the number of guest,g?