Respuesta :

irspow
ECA is supplementary to ACB which means that the two angle sum to 180°

ECA=180-65=115°

Since angles ACB and ECA make a straight line, they have to add together to be 180 degrees. So, all you have to do is set up an equation that equals 180 and solve for the missing value. Your work should look like this. 

65 + x = 180  (Subtract 65 from both sides)

x = 115

Your answer should be that angle ECA = 180 degrees.