Question

the sum of the angles marked

Answer 1

given = L II M
construction = draw a line p parallel to l and m bisecting angle B

now ,
         angle 1 + angle 2 = 180 degree ( sum of co-interior angle ) ------(1)
         angle 3 + angle 4 = 180 degree ( sum of co-interior angle ) ------(2)
      
          adding (1) and  (2)
          angle 1 + angle 2+ angle 3+ angle 4 = 180 +180 
          angle (A+B+C) = 360 degree