standard_description: Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8.
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