Excel Solver - Simaltaneous Equations

1) Why solver here? which variables you want to change? and what would be your goal (max Q? min Re? f=somepredefinedvalue?)

2) How about 2000<Re<=4000 ?

If you want just to solve calculate both scenarios and check for both if Re (you will have it already calculated) was within assumed range - if yes keep solution, if not - discard it.

It is an interesting set of equations (looks like fluid mechanics??). I see that Q is a function of f, f is a function of Re, and Re is a function of Q. In effect, this makes a nice "circular" function where Q is a function of f and f is a function of Q.

When I see a set of equations with circular reasoning like this, my first thought is often to use a simple iteration or successive approximations technique. Pick a reasonable "initial guess" for one of the variables (I would probably guess Q first -- especially if this is fluid mechanics). From this initial guess for Q, use EQ 2 to calculate Re, then plug that value for Re into 3.1/3.2 to get f. From this value for f, calculate a new value for Q from Eq 1. From this new value for Q, you can calculate a new value for Re and continue iterating until successive approximations are not changing (or are obviously diverging). It is kind of hard to test on this side of the internet without the expected values for the other quantities present in the equations, but this kind of approach often works quite well for this kind of problem.

If this is a homework problem and you are required to use Solver, let us know and we can look at that approach as well.