P•X=-10

I already know the answer but what why is P -10?

Me complete this proof! prove that a quadrilateral is a square. me with the steps for this proof.

The length of the line segment joining the midpoints of sides ab and bc of the parallelogram abcd is 10. find the length of diagnol ac

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