Question

Two angles in a triangle add up to 115° what is the size of the third angle

Answer 1

If you want to find the last angle, you need to subtract the full degrees of angles by the angles you already have. 

So this is what you equation should look like:
180 - 118 = 
(180 is the full amount of angles.)

So the answer would be 180 - 118 = 62
So the answer to your question would be that the last angle is 62 degrees. 

Answer 2

65 degrees that's it man