Question

18)
8x + 2
70° 60°
20)
x + 51
80° 60°

Explanation:

Step1: Sum of triangle angles

$8x + 2 + 70 + 60 = 180$

Step2: Simplify the equation

$8x + 132 = 180$

Step3: Solve for x

$8x = 48 \implies x = 6$

Step4: Find vertical angle

Vertical angle of $80^\circ$ is $80^\circ$

Step5: Sum of triangle angles

$x + 51 + 80 + 60 = 180$

Step6: Simplify the equation

$x + 191 = 180$

Step7: Solve for x

$x = -11$

Answer:

For problem 18: $6$
For problem 20: $-11$