Answer:
a = 25
Explanation:
The exterior angles of a polygon sum to 360°
Sum the exterior angles and equate to 360
a + a + 40 + 51 + 55 + 54 + 2a + 60 = 360, that is
4a + 260 = 360 ( subtract 260 from both sides )
4a = 100 ( divide both sides by 4 )
a = 25