# data[].attributes.body
http://www.mathplayground.com/wpdatabase/Addition_Subtraction_3Digit_1.htm

http://www.math-play.com/multi-digit-addition-basketball-game/multi-digit-addition-basketball-game.html

http://www.softschools.com/math/subtraction/3_digit_subtraction/3_digit_subtraction_with_regrouping/