If you would like to know how many total hours did Jeff work today, you can calculate this using the following steps:
4 2/3 hours in the morning + 3 3/4 hours in the afternoon = 4 2/3 + 3 3/4 = 14/3 + 15/4 = 56/12 + 45/12 = (56 + 45) / 12 = 101/12 = 8 5/12 hours
Jeff worked 8 5/12 hours in total.
