Yes, you can use multiple equations in a solve block. But....
In general you have to solve for exactly as many variables as you have equations (vector equations or variables modify this).
All variables used in the solve block must be defined prior to the solve block. Those with known values must be defined with those values, those whose values are not known (are variables for which you are solving) must be defined with guess values.
You have a units problem in the equations for Aw and Pw. You are multiplying Lmin by a foot, but Lmin is already defined as a length.
You have an inexplicable constant of 1ft appearing in various places in the equations. I suspect that that really should be a variable, defining an aspect of the system.
In general where one variable is simply a function of other variables it is better to just make a function definition for it rather than try to implement the relationship as a solve blcok constraint. Remember, = is a predicate and never defines anything. That remains true in a solve block, where it is merely a constraint.
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� � � � Tom Gutman