Answer: 40 minutes
Step-by-step explanation: The two of them could rake it in 24 minutes
Let x represent the minute the assistant can work alone and y represent the minutes Gary can work alone
Let the job required to be done be 1, then Gary can rake 1/y and the assistant can rake 1/x
i.e 1/x + 1/ y = 1/24
substituting the time it will take the assistant
⇒ 1/60 + 1/y = 1/24
1/y = 1/24 - 1/60
1/y = 1/40
therefore y = 40 minutes
i.e it will take Gary 40 minutes