note the shared library is located in /usr/lib/lp_solve/ not /usr/lib so you have to pass -L /usr/lib/lp_solve/ to your link command line that it pics it up.
note the shared library is located in /usr/lib/lp_solve/ not /usr/lib
so you have to pass -L /usr/lib/lp_solve/ to your link command line that it pics it up.