The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(6²) + 2π(6 x 9)
sa = 2π(36) + 2π(54)
sa = (2 x 36)π + (2 x 54)π
sa = 72π + 108π
sa = 180π

A rectangle is a parallelogram containing four right angles. Opposite sides (a = c, b = d) are equal and the perimeter is the sum of the lengths of all sides (a + b + c + d) or, comonly, 2 x length x width. The area of a rectangle is length x width. A square is a rectangle with four equal length sides. The perimeter of a square is 4 x length of one side (4s) and the area is the length of one side squared (s²).

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

9a + 7 = -4 - 6a
9a = -4 - 6a - 7
9a + 6a = -4 - 7
15a = -11
a = \( \frac{-11}{15} \)
a = -\(\frac{11}{15}\)

A trapezoid is a quadrilateral with one set of parallel sides.

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

6a - 6a = 0a