-- Candy takes 57 minutes to do the whole job ==>
She does 1/57 of the job every minute.
-- Tim takes 114 minute to do the whole job ==>
He does 1/114 of the job every minute.
-- If they work together, they do (1/57 + 1/114) of the job every minute.
We have to add those fractions.
The least common denominator is 114.
(1/57 + 1/114)
= (2/114 + 1/114)
= 3/114 = 1/38 .
Working together, Candy and Tim do 1/38 of the job every minute.
So it takes them 38 minutes to do the whole job together.