Answer:Step-by-step explanation:By observation, you can see that the irregular polygon can be split into 4 triangles (see attached image). We know that the sum of the internal angles of 1 triangle is always 180 degrees. Hence the sum of all the internal angles of the polygon is, 180 degrees x 4 triangles = 720 degrees.Therefore Angle B, = sum of internal angles - sum of all other known angles= 720 - (133 +102+117+90+170) = 108 degrees.