We have three problems that are basically the same, so let's try to come up with a general formula.
As you've observed in the previous problems I've helped you with, the angle cut off by a tangent and a chord is half that of the arc they cut off. So, in the first two problems, if we let the angle we're given be

, we have

.
Then, by the straight-line angle rule (angles that together form a straight line sum to 180 degrees),

. Applying the first rule again,

.
Applying these formulas, for the first question,

,

, and

.
For the second problem,

,

, and

.
For the third, the variables are positioned differently, so we replace

with

(because

is now the arc cut off by our given angle) and

with

.
So,

,

, and

.