Answer
a) $50^{\circ}$
b) $25^{\circ}$
Work Step by Step
To use the protractor, we subtract the smaller angle at one end of the protractor from the larger angle at the protractor. Doing this, we find:
Case A:
$$ \angle 2= 180^{\circ}-130^{\circ} \\ \angle 2 = 50^{\circ}$$
Case B:
$$ \angle 4 = 155^{\circ}-130^{\circ} \\ \angle 4 = 25^{\circ}$$
