Answer:
120 degrees
Step-by-step explanation:
Remember that the interior angles of a triangle always add up to 180 degrees. We know that two of the angles (45 and 15) add up to 60 degrees. Now we just have to subtract the 60 degrees we have from the 180 degree total in order to get the measure of the missing angle.
180 - 60 = 120
Therefore... the answer is 120 degrees