Answer
$\angle$1 + $\angle$2 = $\angle$3 + $\angle$4
Hence proved
Work Step by Step
Sum of all angles of a quadrilateral = $360^{\circ}$
Sum of linear angles on a line = $180^{\circ}$
HENCE
$\angle$SRQ + $\angle4 + \angle$QTS + $\angle$3= $360$
THUS (180- $\angle$1)+$\angle$4 + (180-$\angle$2) +$\angle$3=$360 \approx 360 + \angle$4 + $\angle$3 -$\angle$1 - $\angle$2 =$360$
since $ (360-360=0)$
BY taking all the negative terms to The Right
= $\angle$1$ + $$\angle$2$ = $$\angle$3 + $\angle$4 Hence proved
