Respuesta :

There are 180 degrees in a triangle when you add the measures of the angles together.  So...
102 + 39 + x = 180
141 + x = 180
x = 39
ookiku
it's 39 because a triangle adds up to 180. so you can add 39 and 102 and get 141 and subtract that from 180, getting 39. the missing angle