If Joe finished half of his homework questions at school and completed one-third after practice, how many problems did Joe start with if he has 13 to finish

Answer: 78 problems

Step-by-step explanation:

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

If he has 13 to more to finish, that means

x/6 = 13

x = 13*6 = 78 minutes