Properties of addition/Adding and Subtracting within 1000
http://www.floridastudents.org/PreviewResource/StudentResource/105831
3 digit subtraction with regrouping
http://www.softschools.com/math/subtraction/3_digit_subtraction/3_digit_subtraction_with_regrouping/
http://www.floridastudents.org/PreviewResource/StudentResource/105831
3 digit subtraction with regrouping
http://www.softschools.com/math/subtraction/3_digit_subtraction/3_digit_subtraction_with_regrouping/