Question:
In the adjoining figure, what value of x will make AOB a straight line?
Solution:
AOB will be a straight line if
$3 x+20+4 x-36=180^{\circ}$
$\Rightarrow 7 x=196^{\circ}$
$\Rightarrow x=28^{\circ}$
Hence, x = 28 will make AOB a straight line.