this is a isosceles triangle. all sides degrees added together (triangle) is equal to 180.
we know one side is 55°, and since its isosceles, it will be congruent on both sides. so there are 2 55°.
since the sum of all angles is 180°, the equation will be 55°+55°+x=180
combine like terms (55+55), which equals to 110.
last, 180-110 = 70
so the answer will be x = 70°
