To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

6a x 7b = (6 x 7) (a x b) = 42ab

An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 60° - 62° = 58°

So, d° = 62° + 58° = 120°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 60° = 120°

The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

a² + 4a - 30 = 4a - 5
a² + 4a - 30 + 5 = 4a
a² + 4a - 4a - 25 = 0
a² - 25 = 0

Next, factor the quadratic equation:

a² - 25 = 0
(a - 5)(a + 5) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a - 5) or (a + 5) must equal zero:

If (a - 5) = 0, a must equal 5
If (a + 5) = 0, a must equal -5

So the solution is that a = 5 or -5

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.

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).