Final answer:
The question 'Find mST' cannot be answered without additional context or details. In mathematics, especially geometry, specific information is required to apply mathematical rules and theorems, which is missing in this case.
Step-by-step explanation:
The question 'Find mST' appears to be incomplete as it does not provide sufficient details or context to accurately determine what mST refers to. In mathematics, determining the measure of an angle or a segment usually requires additional information such as a diagram, description of a shape, or a set of equations. This information is needed to apply mathematical rules and theorems to find the required measurement.
Without the necessary context or additional details, it is not possible to select the correct answer from the options provided (a) 180°, (b) 142°, (c) 153°, (d) 134°. If the question pertains to finding the measure of an angle in a triangle, for example, one would typically use the fact that the sum of angles in a triangle is always 180 degrees. However, with the information given, no such conclusion can be drawn.
Please provide more detail or context regarding mST, such as the geometrical setup or relevant equations, so I can assist you better.