Answer: the measure of the third triangle is 75 degrees.
Explanation:
Let the measure of the third angle be x degrees.
The sum of the three angles in a triangle is 180 degrees.
One of the angle measures 30 degrees, and the second angle measures 75 degrees. Therefore,
30 + 75 + x = 180
105 + x = 180
Subtracting 105 from the left hand side and the right hand side of the equation, it becomes
x = 180 - 105 = 75 degrees