When the product of 10 and 15 is divided by the sum of 10 and 15 what is the quotient

Which expression is equivalent to √ -80?

When you arrive at the lake, your friend realises he hasn’t got any swimming trunks. you need to ride to a sports shop. the sports shop is 8350 metres away. how many metres is it to cycle there and back?

You got a job selling magazines door-to-door. you are paid $100 per day plus $1.50 for each magazine you sell. which recursive formula models this situation?