standard_description: Determine the unknown whole number in an addition or subtraction equation relating to three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = �� – 3, 6 + 6 = ��.
problem_activity: Problem 2
Pre-unit
There are 9 ducks in the pond.
There are 7 ducks on the grass.
How many ducks are on the pond and in the grass?
Show your thinking using drawings, numbers, or words.


aligns: no