use pythagoras theorem to find the missing side, then find the an angle using the sine rule. at this point you will only have one angle left. using the law that sum of all angles of a triangle add up to 180⁰, you can do 180⁰- ( [the angle you found by the sine rule] + 90⁰) hope this wasn't too complicated :)
i did (b) as an example attatched (2 photos bc it couldn't fit it all)