Mathcad can manange some symbolic solutions of non-linear equations, but it is still only a computer programme so can't work miracles. But it can try a lot of methods and approaches so will have a go. It does help if you have a good idea of the sort of answer you would expect. It is easy to make the system of equations just that little bit too fancy and as a consequence loose all chance of a solution.
You also have to beware of MuPad's German origins, so while it has precision, it can also be pedantic. Maple appears to have the opposite American view, often providing the 'common' answer, even if it is wrong (think integral (1/x) passing through zero..)
Start with a system of 2 equations, and build up to three, then four.