Erin puts 3 small cans , 4 medium cans , and 5 large cans on a shelf . how cans does she put on the shelf

To find out the sum (answer) you would just add up all of the cans since they are all cans, no matter the size. 3+4+5 = 12. Therefore, Erin puts 12 tots cans on a shelf

Hope I helped and good luck!