Answer:
s = 87
Explanation:
Let´s call the missing internal angle "a"
a + (s + 49) = 180
a + s = 180 - 49
a + s = 131
a = 131 - s
The sum of the internal angles of a triangle = 180°
(s-38) + s + a = 180°
(s-38) + s + (131-s) = 180
s + s - s + 131 - 38 = 180
s + 93 = 180
s = 180 - 93
s = 87