I hope this is right but:
Let n=number of full time employees
260<=20+n*40
260-20<=N*40
240<=n*40
n>=240/40
n>=6 full time employees
which means he would have to hire at least 6 or more fully time employees
Though I'm not sure if the attached file is the graph you are looking for
Let n=number of full time employees
260<=20+n*40
260-20<=N*40
240<=n*40
n>=240/40
n>=6 full time employees
which means he would have to hire at least 6 or more fully time employees
Though I'm not sure if the attached file is the graph you are looking for