CCSS.MATH.PRACTICE.MP1 Make sense of problems and persevere in solving them.
CCSS.MATH.PRACTICE.MP3 Construct viable arguments and critique the reasoning of others.
CCSS.MATH.PRACTICE.MP8 Look for and express regularity in repeated reasoning.
http://www.corestandards.org/Math/Practice/ - Click link for more information on these standards.