Respuesta :

We use angle sum property of triangle here :

sum of three angles = 180 degrees

118.6 + 42.3 + third angle =180

160.9 + third angle =180

third angle =180-160.9

third angle =19.1 degrees

all Triangles have a complete measure of 180 degrees so 180- 118.6-42.3 =19.1

the answer is C!