Break up the problem into two parts: 1) find the surface area of the sides of the cylinder and 2) find the surface area of the top or bottom and multiply your result by 2.
Part 1: Imagine that you cut the side of the cylinder parallel to its axis once and then open up this shape to form a rectangle. The length of this rectangle is equal to the circumference of the cylinder times the height/length of the cylinder parallel to its axis: A1 = 2 pi (7 units) (3 units), or 42 pi square units.
Part 2: The total area of the two ends of the cylinder is 2 (pi [7 units]^2), or 98 pi square units.
Add these two areas together to get the total surface area of the cylinder.
