all the angles in a triangle added together = 180 degrees In your problem they probably give you at least one angle. so by using that one angle you can find the rest of the angles in the triangle.
the 3 sides have to add up to 180 degrees. if one side is 60 degrees and the other is 60 degrees what is the other side? it is 60 because if you add 60 plus 60 equals 120. then you subtract 180 minus 120 which equals 60.