Teachers could pose problems such as the following:

Rex had 12 pieces of candy. During the day, he ate some of the candy. By the end of the day, he had 4 pieces of candy left. How many pieces of candy did he eat that day? Show how you know your answer is correct.

There were eight bears eating at the zoo. Then nine more bears came to eat. How many bears were eating at the zoo? Show how you know your answer is correct.