For 3(a), there are only 2 answers because the variable is theta. For 3(b), there are 4 answers because the variable is 2x so we need to add 360 degrees to the two basic answers. I included the negative answer for 3(b) because cosine is positive in the 4th quadrant and the angle could also be a negative answer. This answer was ultimately rejected because it's not in the specified range.