At work Keith spends one-fifth it his time in planning and buying merchandise. He spends seven-twelfths of his time in customer service and one-twentieth of his time training the staff. This leaves him ten hours to deal with the accounts. How many hours does he work each week?

60 Hours

Step-by-step explanation:

First let's get all fractions equivalent.

1/5 7/12 1/20 We can make the common denominator 60

12/60 35/60 3/60

So these three parts of his week take up 50/60 or 5/6 of his time. That means he only has 1/6 left. The question also tells us after all of this he only has 10 hours left, so 1/6 = 10 hours. If you have 1/6 of something how do you find one whole? or 6/6. You multiply it by 6. so 10*6 = 60, which means every week he works 60 hours.