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 < sign and the answer on the other.

2x - 5 < \( \frac{x}{-4} \)
-4 x (2x - 5) < x
(-4 x 2x) + (-4 x -5) < x
-8x + 20 < x
-8x + 20 - x < 0
-8x - x < -20
-9x < -20
x < \( \frac{-20}{-9} \)
x < 2\(\frac{2}{9}\)

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.

(3a)(7ab) - (2a²)(4b)
(3 x 7)(a x a x b) - (2 x 4)(a² x b)
(21)(a¹⁺¹ x b) - (8)(a²b)
21a²b - 8a²b
13a²b

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° - 27° - 69° = 84°

So, d° = 69° + 84° = 153°

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° - 27° = 153°

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 perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 13cm + 15cm + 10cm = 38cm