Total number of students graduating = 450
68% of 450 are going to college which is =

= 306 students are going to college
14% of 450 plan to start working =

= 63 students will start working
So total students who are going to college and working are =

So, the students do not know what they are going to do yet are =

Hence, 81 students do not know what they are going to do yet.