There are three machines, each working at a constant rate (those rates may be different or the same — the problem doesn't specify). The question asks for two quantities: the number of marbles produced by Machine A in one hour and the number of marbles produced by all three machines collectively in one hour. The relevant equation needed for this question is Rate X Time = Work.
First Column:
It is most useful to begin with the last piece of information presented: Machine C can do a full lot of 90 marbles (Work) in 45 minutes (Time). Machine C, then, works at a Rate of (90 marbles) / (45 minutes) = 2 marbles / minute, and produces 120 marbles in one hour (2 marbles/minute x 60 minutes).
In addition, the last sentence also states that Machine C is twice as fast as Machine A. If Machine C produces 2 marbles per minute, then Machine A must produce 1 marble per minute, and 60 marbles per hour (1 marble/minute x 60 minutes). The answer to the first part of the question is 60.
Second Column:
The second part of the question asks for the number of marbles all three machines produce in an hour when working together. This will be the sum of the marbles each machine produces in an hour. You already know that Machine A produces 60 marbles per hour and Machine C produces 120 marbles per hour, so A + C = 180. The total marbles will be 180 plus the number produced by Machine B.
Before trying to calculate the precise number of marbles produced by Machine B, glance at the answer choices. Only one answer is greater than 180. The answer to the second part of the question is 228.
First Column: The correct answer is (C) 60.
Second Column: The correct answer is (F) 228.
