Answer:
b= 70
Step-by-step explanation:
The sum of the opposite interior angles of a triangle is equal to exterior angle.
a+b = 140
We know that a = b since PQ = RQ The angles opposite the equal sides in an isosceles triangle are equal
b+b = 140
2b =140
Divide by 2
2b/2 =140/2
b= 70
