PLANE GEOMETRY (Do NOT answer the same set of questions. There are other sets of questions I posted. Answer those. Please.)

Analyze and solve for unknowns in every problem given. Submit the scanned copy of your solutions. Digital solutions are highly encourage. If written solutions, use a black ballpen (if available) and white bond paper. STRICTLY NO ERRASURES ALLOWED!

Problem 18. Given triangle ABC, point E is along side AC and point D is along side BC. Line BE and AD are the angle bisectors of angle B and A respectively. If the angle BEC = 750 and angle ADC = 840, find the ACB.

Problem 19. The distance between the center of the circles which are mutually tangent each other externally are 10 cm, 12 cm and 14 cm respectively. Find the area of the largest circle.

Problem 20. Two circles are concentric. The chord of the bigger circle is tangent to the smaller circle and measures 10 cm. What is the area outside the smaller but inside the bigger circle?