First, find n. We know that the base angles of an isosceles triangle are equal and that angles in a triangle add up to 180°. This means that:
110 + n + n = 180° - now simplify:
110 + 2n = 180° - subtract 110 from both sides:
2n = 180 - 110 - simplify again:
2n = 70° - divide both sides by 2:
n = 35°
Now we know n, we can find m. The whole diagram is a triangle with angles of 90°, 35° (n) and the final angle can be split into m + n (m + 35°). This means that 125°+ m + 35 = 180° (125 came from doing 90 + 35):