What is the sales tax for a purchase of $8 if the tax rate is 5 percent?

Based on what i know about mean, this doesn't add up.

The estimated number of people to attend the last bengals game of the season was 2000. the actual number of fans attending was 1200. by what percent did the estimate differ from the actual?

The figure below shows rectangle abcd and the triangle eca on a coordinate plane.which of the following expressions represents the perimeter of triangle of triangle eca in units