18 students are wearing colored tops for a game.
There are 7 red tops, some green tops, and 5 blue tops.
Find the addition sentence that matches this story.
How many green tops are there?
19 first graders went to a sports day. 3 of them did the long jump, 11 ran in a race, and others did the high jump.
Answer the following questions to complete the addition expression.
What number belongs in the first box?
How many students did the high jump?
Find the three numbers from 4, 1, 7, 9, and 2 whose sum is 10.