 Hi and welcome to the session. Let us discuss the following question. The question says in figure 10.39, this is the figure 10.39. A, B, C and D are four points on a circle. A, C and B, D intersect at a point E such that angle B, E, C is equal to 130 degree and angle E, C, D is equal to 20 degree. Find angle B, A, C. Let us now begin with the solution. In the question we are given that angle B, E, C is equal to 130 degree and angle E, C, D is equal to 20 degree. We have to find angle B, A, C. Now angle C, E, D plus angle B, E, C is equal to 180 degree since they are forming linear pair. Now substitute the value of angle B, E, C in this equation. So we have 130 degree plus angle C, E, D is equal to 180 degree. This implies angle C, E, D is equal to 50 degree. So this angle is of 50 degree. Now consider triangle E, C, D. In triangle E, C, D angle E, E, D plus angle E, C, D plus angle C, D, E is equal to 180 degree because sum of all angles of a triangle is 180 degree. Now substitute the value of angle C, E, D and angle E, C, D in this equation. As substituting the values we get 50 degree plus 20 degree plus angle C, D, E is equal to 180 degree. Now this implies angle C, D, E is equal to 110 degree. Now angle C, D, E and angle B, A, C are equal because these are angles in the same segment and we know that angles in the same segment are equal. So angle B, A, C is also equal to 110 degree. Hence our required answer is 110 degree. This completes the session. Bye and take care.