Question

How do I find value of each letter without measuring it?

Answer 1

$p=125^0(\text{vertically opposite angles are equal)}$$\begin{gathered} p+q=180^0(sum\text{ of angles on a straight line)} \\ 125+q=180 \\ q=180-125 \\ q=55^0 \end{gathered}$$\begin{gathered} r=q(\text{corresponding angles are equal)} \\ r=55^0 \end{gathered}$