geometry

The inside angles of a triangle sum to 180 degrees    29 + 82 + 'other angle' = 180

         'other angle' = 180 - 29 - 82        solve for 'other angle'

then:

'other angle'  + x    form a straight line

'other angle' + x = 180     solve for 'x'

x is an exterior angle, there is a rule that says

so x = 29 + 82 = 111