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: Construct a system of two linear equations where
$${(-2,3)}$$
is a solution to the first equation but not the second equation and where
$${(5,-2)}$$
is a solution to the system.


aligns: no