I really need help on this, please help out

Volume of a cylinder with a radius of 13 in and height of 30 in

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

Imogene invested $8,000 in a bank account that pays 8 percent simple interest at the end of each year. her friend invested the same amount in stocks where the growth of the investment is represented as 2,000 times the square root of 2 less than the time lapsed in years. if y1 and y2 represent the amount earned in dollars and t is the time lapsed in years, which system of equations correctly represents the situation?