Hello, BG5965!

You're expected to know these rules:

[1] If parallel lines are cut by a transversal,

. . .the corresponding angles are equal.

[2] If parallel lines are cut by a transveral,

. . .the alternate-interior angles are equal.

[3] A central angle is measured by its intercepted arc.

[4] An inscribed angle is measured by one-half its intercepted arc.

1) In the figure: .

We are given: .

Then: .

And: .

Therefore: .

2) In the figure: .

We are given: .

Then: .

And: .

Therefore: .

3) In the figure: .

We are given: .

Then: .

And: .

Therefore: .