Oh, I could help you
For the first leak, we lost 20 minutes, that means in 1 minute we can complete 1/20 of this bucket.
For the second, it is the same, we can fill 1/35 of this bucket in 1 minute.
Now, we have two leaks and in 1 minute we can fill 1/20+1/35= 11/140
That means we need 140/11 minute.
Have fun