Whenever an equation asks for when it will take x (or m in this case) amount of things or time you should know that there will be 2 different equations that have to equal each other
The equation will be 250.50 - 35m = 300 - 45.25m
The 35m is being subtracted from 250.50 because they are losing money each time they spend. This also applies to 45.25m
Also 35m and 45.25m are variables because it says they spend that much money each month. They don't specify how many months, so we have to put a variable after it.
An echo is formed as a result of reflection of the original sound which returns to the listener. You might have experienced Echo in an EMPTY ROOM but no echo is produced after the room is occupied. To avoid echo from being produced the echo has to be absorbed. Echo in a cinema theatre is absorbed by the WALLS of the theatre.
They are not plain. The walls are corrugated or shaped to form tiny holes or empty spaces to ABSORB the ECHO. Modern Theatre's have ABSORBENT materials sticked to the walls of the theatre.