An employee at the craft store counted the number of red buttons in each bag of mixed buttons. How many bags had at least 36 red buttons?
Stem | Leaf 
3 | 0, 1, 7, 7
4 | 3, 8
5 | 4, 5, 9
6 | 0, 3, 8
7 | 3, 5, 6, 7, 7
8 | 0, 1, 5, 7
9 | 0, 0
Find the row with stem 3. Count all the leaves greater than or equal to 6.

Count all the leaves in the rows with stems 4, 5, 6, 7, 8, and 9.

You counted 21 leaves, which are blue in the stem-and-leaf plots above. 21 bags had at least 36 red buttons.