Common Core wants the kids to think about, discuss, and justify (not just solve) and this activity does all that. In this true false sort, the students pair up and determine if the statements given to them or true or false. If they are false, they have to justify/explain their decisions. I am always amazed at how much the kids learn during the sorting games. When they start discussing and having real math discussions, they take their depth of knowledge to a much higher level.
"When you subtract two negative integers, your answer will sometimes (but not always) be negative."
"Zero is a positive number"
"-8 ÷ (-2) • 5= -20"