How do you write these as an algebraic expression?

For 9, we have multiplying (multiplication) of h and the sum (addition of base1 and base2). Since it doesn't say to multiply them individually, we have h*(base1+base2)

For 10, we have the surface area = 2 times pi * r^2 (the square of the radius) plus the product (multiplication) of pi, the radius, and the height =
2*(pi*r^2)+(pi*r*h)

20000 as first it increases by 2500 then by 5000 so next it will increase by 10000