Answer: 150

Solution:

Let Tom's swimming speed be $s$ miles per hour. Then he runs at $5s$ and bicycles at $10s.$ The total time in hours is $$\begin{aligned} &\frac{0.5}{s} + \frac{30}{10s} + \frac{8}{5s} \\ &= \frac{0.5 + 3 + 1.6}{s} \\ &= \frac{5.1}{s} = 4.25, \end{aligned}$$ so $s = \frac{5.1}{4.25} = 1.2$ miles per hour.

He bicycles at $12$ miles per hour, so the ride takes $\frac{30}{12} = 2.5$ hours, which is $150$ minutes.