Mrs. quirk buys 1 quart of milk. michael drinks 2/7 quart of it. joel drinks 1/3 quart of it. how many quarts of milk are left? show your work !

First, let's find the least common denominator, or LCD of both of them. of the two fractions. 

7 and 3 both go into 21.

Now, multiply the two fractions to get the LCD. Remember, whatever you do to the bottom you must do to the top.

2/7 * 3/3 = 6/21 quart
Michael drank 6/21 quart of milk.

1/3 * 7/7 = 7/21 quart
Joel drank 7/21 quart of milk.

Add together 7/21 and 6/21 to get 13/21, the total amount of milk they both drank from the quart.

Now, subtract 13 from 21 to find how many quarts are left. Simplify if necessary.
21 - 13 = 8/21 quart

Since you can't simplify, there is 8/21 quart of milk left.
Hope I helped! <3