If Fred is x years old, and his sister is half as old, how old would his sister be in five years

Answer question above and explain each step : )

Find the values of y: 3y^3(y^2+ 2/3y)=0

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.