Answer:
24 birds.
Explanation:
We have been given that Emily and her friends went to the park. they saw 15 robins and 9 blue jays. We are asked to find the number of birds and explain how you decided what number sentence to write.
Since there are 15 robins and 9 blue jays, so we can get total number of birds by adding 15 to 9.

Since we are asked to find total number of birds, so we can find total birds by addition only.
Therefore, Emily and her friends saw 24 birds.