what makes these tough is that you have to remember that the total of the angle is known, you know it to be 180 ° , so since you know the total just set all the part equal to that
180 = 4x + 6x-20 + 5x - 10
now you can slove for x with your mad algebra skilz :) if you don't have those yet. it's okay.. most people don't :D Super hero's and math whizzes only, seem to have those. :D
180 = 15x -30
210 = 15x
14 = x
now that we know what x is , plug it into the angle BCE
