Mathcad 7 returns wrong result

I agree, the symbolic solver should tell you:

where the error message is: "No solution was found".

On the other hand:

That's pretty close to 0... I guess the real answer is only found from the other side:

The problem is similar to:

I must admit that the numeric processor does slightly better:

But it fails to recognise an answer that's close to the limit:

Success!

Luc

Nobody is perfect and symbolic calculations are not the main arguments for using Prime. For symbolics you may have a look at Maple or Mathematica (or even MatLab with a more powerful muPad under the hood).
Primes legacy symbolic sometimes (quite often) outrules the new one

but not always:

but OK, 204.50 at least is closer to infinite that 33.58 🙂