I have the following two equations:

(1/2x) * LN (z/(z+3600)=880

and

(1/2x) * LN (z/(z+6400)=1350

How can I resolve x and z from these two equations?

I could do this by iteration, but I prefer formulas like x=....... and z=........

I salute you if you know how to resolve this! (Clapping)