Question

from the figure given below, find

Answer 1

Given=a=20 degree

2a=20x2=40 degree

a+b=90 degree

we have to find b

2b=?

linear pair

2a+2b=180

40+2b=180

2b=180-40

2b=140

b=140/2

b=70

Answer 2

If a= 20

In this figure, all angles lie on a straight line.
Therefore,
a + a + b + b = 180
20 + 20 + 2b = 180
40 + 2b = 180
2b = 180 - 40
b = 140/2
b = 70