Step 1: Recall formula for maximum shear stress.
\[
\tau_{max} = \frac{\sigma_1 - \sigma_2}{2}
\]
Step 2: Substitute values.
\[
\sigma_1 = 100 \, MPa, \sigma_2 = 50 \, MPa
\]
\[
\tau_{max} = \frac{100 - 50}{2} = \frac{50}{2} = 25 \, MPa
\]
Final Answer:
\[
\boxed{25.0 \, MPa}
\]