Suppose x|mn where m, n, x ? z and gcd(x, m) = 1. prove that x|n.

Iam so stuck. what is the worked out answer for this question?

Each of the walls of a room with square dimensions has been built with two pieces of sheetrock, a smaller one and a larger one. the length of all the smaller ones is the same and is stored in the variable small. similarly, the length of all the larger ones is the same and is stored in the variable large. write a single expression whose value is the total area of this room. do not use any method invocations.

Acontainer full of water weighs 15.5 lbs. when ¼ of the water is poured out, the container now weighs 12 ½ lbs. how much does the container weigh when empty?