Answer :
If she has finished 20%, she still has 80% to do. So just calculate .8 times 150.
80% more
80/100 simplify = 4/5
4/5 of 150 = 120
She has to grade 120 more
80/100 simplify = 4/5
4/5 of 150 = 120
She has to grade 120 more
