Subtraction within 20 HUGE differentiated first grade math unit that makes subtracting fun with games, worksheets, and activities! This JAM-PACKED unit is filled with 162 pages of everything you need to teach subtraction within 20. This pack covers 5 main standards/concepts: subtraction within 20, number lines (counting back), word problems, backwards doubles, and mixed review (addition/subtraction review).Get this in the First Grade Math Units 1-9 BUNDLE to save a ton!**Please click the green P