U=3xk+6xw-6xv; for xi really need with this can someone me step by step?

Sum is 17 and their difference is 3

I’m on question 7 it says a covered water tank is in the shape of a cylinder the tank has a 28 inch diameter and a height of 66 inches to the nearest square inch what is the surface area of the water tank

  cassidy wants to cut the yellow fabric into strips that are 0.3 yards wide. how many strips of yellow fabric can cassidy make? yellow fabric 16 yards for $108.00.