How do i find the original price of an item from the tax rate and tax price?

Can someone explain the elimination method to me for this problem?

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

The means and mean absolute deviations of the individual times of members on two 4x400-meter relay track teams are shown in the table below. means and mean absolute deviations of individual times of members of 4x400-meter relay track teams team a team b mean 59.32 s 59.1 s mean absolute deviation 1.5 s 245 what percent of team b's mean absolute deviation is the difference in the means? 9% 15% 25% 65%