Question

How do I work out this problem?

Answer 1

First we need to find ∡PRQ. To do this we can use the fact that the sum of the interior angles of a triangle is 180°:

$180=R+P+Q$
$180=R+40+105$
$180=R+145$
$R=180-145$
$R=35$

Now, we can use the fact that a strait line (like SRQ) is also 180°:
$SRQ=180-R$
$SRQ=180-35$
$SRQ=145$ °