The sum of the angles in a triangle is always 180°. Therefore, the third angle can be calculated as:
\[ 180° - 34° - 87° = 59° \]
Step 3: Determine the value of z
The angle z is the exterior angle to the third angle of the triangle. The exterior angle is equal to the sum of the two non-adjacent interior angles. Therefore:
\[ z = 34° + 87° = 121° \]