I'm giving 20 points! Please help fast! Thank you! How do you determine whether to use a percent, ratio, or rate in any given situation?

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

Apool measures 12.3 feet by 16.6 feet. if the longer wall of the pool has a diagonal of 17.8 feet, what is the volume of the pool? (round to nearest tenth)

Asystem of equations has 1 solution.if 4x-y=5 is one of the equations , which could be the other equation ?