E and pi are 2 famous examples
L = rate of the large hose
S = rate of the small hose
we know the sum of their rates deliver the swimming pool filled up in 35 minutes, thus L + S = 35.
now, the large hose can do it in 60 minutes, that means that in 1 minute, the large hose has only done 1/60 th of the work.
the small hose can do the whole thing in S minutes, that means in 1 minute it has only done 1/S th of the whole work.
and since both of them working together can do it in 35 minutes, then in 1 minute they both have done 1/35 th of the whole job.

Answer:
1st question: C
2nd question: Increasing (the slope)
3rd question: don't understand what's being asked
Step-by-step explanation:
1- 4(n - 1.25)
2- 1(4n - 5)
Hope this help! :)