1. The problem asks for the simplest way to find angle $Y$ in triangle $XYZ$ where $\angle X = 40^\circ$, $\angle Z = 60^\circ$, and side $XZ = 12.0$ cm. 2. Recall that the sum of interior angles in any triangle is always $180^\circ$. 3. Therefore, to find $\angle Y$, we can subtract the sum of the other two angles from $180^\circ$: $$\angle Y = 180^\circ - (\angle X + \angle Z)$$ 4. Substitute the known values: $$\angle Y = 180^\circ - (40^\circ + 60^\circ)$$ 5. Simplify the expression: $$\angle Y = 180^\circ - 100^\circ = 80^\circ$$ 6. This method corresponds to option (b) Subtraction of the two given angles from 180°. 7. Using the Cosine Law or Sine Law is more complex here since we already have two angles and one side, so the simplest method is option (b). Final answer: **b) Subtraction of the two given angles from 180°**