To calculate the are of the sides of a cylinder, you take the circumference of the base, or circle, and multiply it times the height. To calculate the circumference of a circle we use the formula 2*pi*r, or 15pi. We multiply this times 20 to get 300pi cm. If you are using 3.14 for pi, this is 942, or if you are using actual pi, around 942.4777.
A line parallel to the y-axis that passes through (77,88) is x = 77. There is no slope-intercept form of this equation if our coordinate system is based upon a horizontal x-axis and a vertical y-axis.