What is the distance between the points (2,5) and (-4,8)?

Icould really use some with this question.

Awater holding tank measures 105 m long, 50 m wide, and 8 m deep. traces of mercury have been found in the tank, with a concen- tration of 60 mg/l. what is the total mass of mercury in the tank? answer in units of kg.

Match the scale and the actual area to the area of the corresponding scale drawing. scale: 1 inch to 4 feet actual area: 128 square feet scale: 1 inch to 7 feet actual area: 147 square feet scale: 1 inch to 8 feet actual area: 256 square feet scale: 1 inch to 5 feet actual area: 225 square feet area of scale drawing scale and actual area scale drawing area: 3 square inches arrowright scale drawing area: 8 square inches arrowright scale drawing area: 4 square inches arrowright scale drawing area: 9 square inches arrowright