MCQ
In Fig. if lines $l$ and $m$ are parallel, then $x =$
  • A
    $85^{\circ}$
  • B
    $65^{\circ}$
  • C
    $20^{\circ}$
  • $45^{\circ}$

Answer

Correct option: D.
$45^{\circ}$
$l \| m$ Let transversal be n and ​​$\angle1=65^\circ$
$​\angle2=20^\circ$
$​\angle3=\text{x}$
Since,
$l \| m$ and n cuts them so,
$​​\angle1+​​\angle4=180^\circ$ (Co. interior angle)
$65^\circ+\angle4=80^\circ$
$​\angle4=115^\circ\text{(i)}$
​​$\angle4=​​\angle5=115^\circ$ (Vertically opposite angle)
$​​\angle2+​​\angle5+​​\angle3=180^\circ$
$20^{\circ} + 115^{\circ}+ x = 180^{\circ}$
$x = 45^{\circ}$.

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