Task# Finding the unknown in a division equation

Illustrative MathematicsVaries

This task shows an equation that elicits key misconceptions around equations and division. Students will be tempted to identify 3 as the missing number because they are envisioning the related fact: Teachers using this task for discussion will want students to voice ideas leading to both answers, but guide the discussion to some key instructional points: An equal sign indicates that both expressions have the same value, therefore 2 must have the same value as the mystery number divided by 6. Addition and multiplication are commutative, but division is not (so mentally plugging in 3 and dividing 3 by 6 does not give the same result as 6 divided by 3). Students may insist that the 2 belongs on the right side because it is 'the answer.'