for the first one you add the two angles together & subtract them from 180 to get the third. for the second one you subtract 120 from 180 to get angle b & then add angle b and c together & subtract it from 180 to get angle d. for the third one you add the two angles together & subtract the answer from 180 to get the third angle. for the rest you add the angles inside together & set it equal to the angle on the outside.
