Question

What is the value of x

find the value of f​

Answer 1

x = 20 , f = 40

Explanation:

4x and 5x are a linear pair and sum to 180° , then

4x + 5x = 180

9x = 180 ( divide both sides by 9 )

x = 20

then

5x = 5 × 20 = 100° and 3x = 3 × 20 = 60°

the exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.

5x is an exterior angle of the triangle , then

f + 3x = 5x , that is

f + 60 = 100 ( subtract 60 from both sides )

f = 40

Answer 2

x = 20°

f = 40°

Explanation:

4x + 5x = 180°

because a straight line is 180°

so 9x = 180°

1x = 180 ÷ 9

1x = 20

all angles in a triangle add together is 180°

so 7x + f = 180°

1x = 20

7x = 20 × 7

7x = 140°

f = 180° - 140 °

f = 40°