11 numbers are written in a row so that the sum of any three consecutive numbers is 18, and the sum of all the numbers is 64. Find the 6th number

How do i do this activity, is appreciated

An arc subtends a central angle measuring 7pi/4 radians what fraction of the circumference is this arc?

The area of a rectangle is 10 cm^2. one side of the rectangle is x cm. express the perimeter of the rectangle in terms of x and show that this rectangle cannot have a perimeter of 12 cm. the perimeter of the rectangle in terms of x is __ cm