When solving problems like this, opposite angles will be equal to 180 when added together. So, when solving for C, you need to find x. You can do this by adding angles D and B. 3x + 9 + 2x - 4 = 180. 3x +2x + 9 - 4 = 180 5x + 5 = 180 5x + 5 - 5 = 180 - 5 5x = 175 5x/5 = 175/5 x = 35 Now, fill in x in angle A and C. 2x + 3 + C = 180 2(35) + 3 + C = 180 70 + 3 + C = 180 73 + C = 180 73 - 73 + C = 180 - 73 C = 107 The angle measure of angle C is 107. Hope this helps!
