Chapter 3.4, Problem 9CE

To determine

To find: the value of $x$ .

Answer to Problem 9CE

  $x=90$

Explanation of Solution

Given information:

  $\angle A=50°$ and $\angle C=40°$

  

Calculation:

In a triangle, sum of allinterior angles is $180°$ .

Therefore in the given triangle,

  $\angle A+\angle B+\angle C=180°$

Substituting the values of $\angle A$ and $\angle C$ ,

  $50°+\angle B+40°=180°$

  $\Rightarrow \angle B+90°=180°$

  $\Rightarrow \angle B={90}^0$

In the given figure, $\angle B$ and $x°$ form linear pair,

  $\angle B+x°=180°$

Substituting the value of $\angle B$

  $90°+x°=180°$

  $\Rightarrow x=90$

Conclusion:

The value of $x=90$ .