A cylinder is a solid figure with straight parallel sides and a circular or oval cross section with a radius (r) and a height (h). The volume of a cylinder is π r²h and the surface area is 2(π r²) + 2π rh.

The formula for circumference is circle diameter x π:

c = πd
c = 18π

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.

-3y - 7 = \( \frac{y}{-3} \)
-3 x (-3y - 7) = y
(-3 x -3y) + (-3 x -7) = y
9y + 21 = y
9y + 21 - y = 0
9y - y = -21
8y = -21
y = \( \frac{-21}{8} \)
y = -2\(\frac{5}{8}\)

To solve this equation, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

-7c(c - x)
-7(-6)(-6 + 6)
-7(-6)(0)
(42)(0)
0

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².