7560 in the ratio 4:5

Logan wants to know how many skateboards have defective parts. he inspects 20,000 skateboards and keeps track of the number of defects per board. use his probability distribution table to find the expected value for defects on a skateboard.

Is the power produced directly proportional to the wind speed, give reasons for your answer?

3x = 729 solve for x plz . it's urgent. will mark