Answer:
22
Step-by-step explanation:
We subtract their goal by their current amount (1000-403) to get 597. We know the class needs at least 597 more cans. We divide 597 (the total needed) by 28 (students) to get 21.3... cans per student. Since each student brings an equal number of cans, we must bring in 22 cans each, leaving us with 19 extra cans.