Answer:
a = 31
Step-by-step explanation:
The external angle of a triangle is equal to the sum of the 2 opposite interior angles.
a + 48 is an external angle of the triangle, thus
a + 48 = a + 2 + a + 15, that is
a + 48 = 2a + 17 ( subtract a from both sides )
48 = a + 17 ( subtract 17 from both sides )
31 = a
