Question

What is the value of x

Answer 1

D) x = 20

Explanation:

Theorem

The sum of the interior angles of a triangle is 180°

Solution

Add the angles and equate to 180:

⇒ (x + 5) + (7x - 5) + x = 180

Collect like terms:

⇒ x + 7x + x + 5 - 5 = 180

Combine like terms:

⇒ 9x = 180

Divide both sides by 9:

⇒ x = 20

Answer 2

x = 20°

The total sum of interior angles in a triangle is 180°

• x + 5 + 7(x) - 5 + x = 180°

• x + 7(x) + x + 5 - 5 = 180°

• 9(x) = 180°

• x = 20°