The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 3 x 9) + (2 x 9 x 7) + (2 x 3 x 7)
sa = (54) + (126) + (42)
sa = 222

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.

The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 51° - 37° = 92°

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.

-3x + 2 = -1 + 4x
-3x = -1 + 4x - 2
-3x - 4x = -1 - 2
-7x = -3
x = \( \frac{-3}{-7} \)
x = \(\frac{3}{7}\)

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.

3a - 4a = -1a