The exterior angle theorem states that the measure of each exterior angle of a triangle is equal to the sum of the opposite and non-adjacent interior angles.
Remember that the two non-adjacent interior angles opposite the exterior angle are sometimes referred to as remote interior angles.
The exterior angle is m < 2a°, while the remote interior angles inside the triangle are m < (a + 10)° and m < 44°.
The following equality statement reflects the exterior angle theorem:
m < (a + 10)° + m < 44° = m < 2a°
At this point, you could solve for the value of "a" algebraically:
a + 10 + 44 = 2a
a + 54 = 2a
Subtract "a" from both sides:
a - a + 54 = 2a - a
54 = a
Now that you have the value for a = 54, substitute this value into the given angles to know their measures:
m < (a + 10)° + m < 44° = m < 2a°
m < [(54) + 10] + m < 44 = m < 2(54)
m < 64° + m< 44° = m < 108°
Therefore:
m < (a + 10)° = 64°
m < 2a° = 108°