To find surface area of 3D objects, you have to know the area formulas for basic shapes. For example, the area of a circle is and the area of a rectangle is length times width. To find surface area of a cylinder, you will need to know both of those formulas, since the 3D shape involves both circles and rectangles.
Option D would probably be the right choice. Because x is the variable for coins, there would be x amount of quarters, and because there are 150 coins, 150 - x would be the remainder.
and the area of a rectangle is length times width. To find surface area of a cylinder, you will need to know both of those formulas, since the 3D shape involves both circles and rectangles.