ok if ur solving for y...u have ur given 4x+5y>80 and u put 1 in the x stop then u would have 4*1+5y>80 and from there u get 4+5y>80 then u subtract 4 from 4 and 80 so u would get 5y>76 the u divide 5 from 5y and 76 so that should give u y>15.2
and, if u want to solve for x u basically do close to the same thing but put the 1 in the y stop and subtract 5 from 5 and 80 and it gives u 4x>75 and dived 4 from 4x and 75 and this would give u x>18.75 ........I really hope this helps u out