The triangle Is an isosceles triangle which means the two bases will be the same angle. 180° is this sum of all angles in a triangle. If 62 is the right base angle then 62 must be the left base angle since is an isosceles triangle. Add 62 and 62 together then subtract from 180. That would give you 54° as the third angle angle at top. Since you are looking for a Z, we now know that z and 54° are symmetry and equal 180 when added together. We then subtract 54 from 180 to get the angle of z.
