Let x = the total number of problems that Joe started with. Joe finished half of his homework questions at school. This means that he finished 1/2 × x = x/2 of the home work at school. What he has left is x - x/2 = x/2.
He completed one-third after practice. This means he completed 1/3 × x = x/3 after practice The number of problems left altogether would be total number of problems - the the sum of the amount he finished at school and the amount he completed after practice. It would be x -(x/2 + x /3) = x - 5x/6 = x/6
