Are my responses for question 3 right?

Not really.

Step-by-step explanation:

3a

The angles x and 4x form a straight angle (=180 degrees).

so x+4x=180 => 5x=180 => x=180/5 = 36

The angles are therefore 36 and 4*36=144 degrees

3b

Similar to 3a, x-20 and x form a straight angle (=180 degrees)

so x-20 + x = 180 => 2x-20 = 180 => 2x = 180+20 = 200 => x = 200/2 = 100

So the two angles are

x-20 = 100-20 = 80 degrees

x = 100 degrees

where's the diagrams?

ok then what happened.