Top-left: Wealth worship. The landlord is so impressed and intimidated by the bank note that he barely dares to take it.
Middle-left: Impending doom. You can tell that the narrator is experiencing a sense of upcoming catastrophe through phrases like "I judged that there as going to be a crash." The situation the narrator is in also involves danger: "I must swim across or drown."
Top-right: Rags to riches. Taken literally, this expression means going from the poorest to the wealthiest one possibly can be. But in this context, it is more about 'social riches:' the character goes from being insignificant in the eyes of others, to widely influential.
Middle-right: Wealth worship. The landlord is willing to accept any of the narrator's whims simply because he is wealthy, but at the same time, he fears him and his power: "he hoped he wasn't afraid to trust as rich a gentleman as I was."
Bottom: Impending doom. The threatening danger here is expressed by the fact that a "thin crust" is all that keeps the narrator from falling into the crater.
Simple. I assume the ones going to the middle school are currently in 5th grade at the elementary school. You have 126 coming into the middle school from each school. You need to multiply 126 by 4. You get 504. There will be 504 new students at the middle school.
