Some math you'll need for this lab...

δt is just the difference in time.

Let's say we have two times:
14:35:27.8 and 14:36:19.6

Their δt will be just the difference between the two times, or 51.8 seconds.

The equation you'll need to calculate the distance to the focus in kilometers is:

Distance

=

δt

x

Vp x Vs Vp - Vs

...where V_p is the velocity of the p-wave, and V_s is the velocity of the s-wave.

Don't forget to convert that to cm on your map!