In the triangle $XYZ$, we are asked to find the size of angle $YXZ$. The side lengths given are:

• $XY = 8 \, \text{cm}$,
• $XZ = 20 \, \text{cm}$.

Since these are two sides of a triangle and no information about the third side or other angles is given, we can attempt to solve this using the Law of Cosines if more information were available about an additional angle or side.

However, if this is intended as a right triangle (based on typical problems), we could alternatively use trigonometric ratios like the sine, cosine, or tangent if an angle were provided.

Could you provide more details about whether this is a right triangle or if any additional information is provided about the other angles or sides?