2/3
There are 52 weeks in a year, Divide by 2 to know how many total orders the salesman needs to make. (26). after 28 weeks he should have 14 orders done (28/2=14) he is 4 behind so he has done 10 orders so far. 26 orders minus 10 that have been done, the salesman needs 16 more orders.
total weeks remaining is found by 52 total weeks subtracted by 28 weeks completed. 24 weeks remain. 16 orders in 24 weeks =16/24 and is reduced to 2/3