From how you've described it, the total leg length will be constant. So, L2 = 39.79 - L1. That is if you are changing each of the 10 tubes individually and are doing so by directly changing the dimension in the path sketch.
If you were looking for something more complex, you'll have to describe how you're doing what you're doing and what is lacking in the current solution.
Or, are you unsure of how to add the equations to the sketch?