Idont understand answer these questions.

Tom had a total of $220 and he spent $35 on a basketball ticket . what percent of his money did he have left?

The function v(r)=4/3pir^3 can be used to find the volume of air inside a basketball given its radius. what does v(r) represent

Hurry if the population of of an ant hill doubles every 10 days and there are currently 100 ants living in the ant hill what will the ant population be in 20 days