See the image for the drawing Let’s say the side BC is extended till D
1) measure of angle ACD = 105° ( angle ACD is exterior angle) 45 + 60 = 105 2) I found the answer by adding the values of Angle A and Angle B or by using the exterior angle property. 3) I observed that exterior angle property can be used here. Exterior angle property is that an exterior angle of a triangle is equal to the sum of the opposite interior angles.