A tutorial for installing the Solver add-in for Excel can be found here.
If you have Mac Excel 2011, then Solver comes bundled with Excel, and you can add it in using the guide given on the website listed above. Unfortunately, there is a bug in the code which requires an alternative approach to adding in Solver. The alternative approach cannot be found anywhere on the web or in any official documentation. Here is the "trick" if you need it.
I brief Excel Solver tutorial in Financial Management Magazine (January, 2019) can be found here.
It is possible to check your answers using MatLab or R. But a genral purpose sensitivity analysis tool for R and/or Matlab doess not seem to be available. If someone knows of a free one, please let me know.
Matlab LP solver subroutine.
R LP solver in Github.
An R tutorial for LP.