The 3 Reads Protocol
https://exemplars.com/blog/three-reads-protocol-understanding-vs-solving
Math Warm-ups and Weekly Challenges
Figure This! Math Challenges
http://figurethis.nctm.org/challenges/challenge_index.htm
Logic and Puzzle Problems
Julia Robinson Mathematics Festival Math Puzzles
https://jrmf.org/puzzle/
Krazydad Printable Puzzles, Mazes, and More
http://krazydad.com/
Erich's Puzzle Palace
https://erich-friedman.github.io/puzzle/
Daily SET Puzzle Online
https://www.setgame.com/set/puzzle
KenKen Daily Puzzles
http://www.kenkenpuzzle.com/
Printable Math Puzzles
http://www.mathinenglish.com/puzzlemain.php
ThinkFun Downloadable Brainteasers
https://www.thinkfun.com/teachers/brainteasers/