As a sporting goods store, 3/10 of all the items are baseball items and 1/3 of all the items are football items. What fraction of the total number of items in the store are baseball or football items?

Find a common denominator first ... which would be 30

3/10*3 = 9/30 baseball items

1/3*10 = 10/30 football items

10/30+9/30 = 19/30 total football and baseball items

19/30 doesn't simplify, so the answer is 19/30