Solve a variable

You have an error in your equation. There should be a multiplication between gamma.o and the opening parentheses.

To solve for h2 you could use the symbolic "solve" and evaluate the result numerical. But I would vote against using this way as I think that if you are just looking for a numeric result, you should also just use a numeric method.

In Prime you can use the "root" function (either by providing an interval for h.s or by providing a guess value) or you could use a solve block with "find".

Using the symbolic "solve" gives you an ugly looking result because the symbolics treats units as unknown variables and it does not know that kN = kPa*m². But you can evaluate the result numerically.

Using he symbolics may make sense before you define you variables or after you make them unknown for the symbolics using the clear command:

Prime 9 sheet attached