ALCOS 2019 Mathematics Standards:
1. Use addition and subtraction to solve word problems within 20 by using concrete objects, drawings, and equations with a symbol for the unknown number to represent the problem.
a. Add to with change unknown to solve word problems within 20.
b. Take from with change unknown to solve word problems within 20.
c. Put together/take apart with addend unknown to solve word problems within 20.
d. Compare quantities, with difference unknown, bigger unknown, and smaller unknown while solving word problems within 20.
2. Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20 by using concrete objects, drawings, or equations with a symbol for the unknown number to represent the problem.
4. Explain subtraction as an unknown-addend problem.
Example: subtracting 10 - 8 by finding the number that makes 10 when added to 8
8. Solve for the unknown whole number in various positions in an addition or subtraction equation, relating three whole numbers that would make it true.
Example: determining the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = ? – 3, and 6 + 6 = ?