Illustrative Math absent lessons and additional practice:
khanacademy.org/math/8th-grade-illustrative-math
Illustrative Math additional help:
im.kendallhunt.com/MS/students/3/index.html
Combine Like Terms
https://www.quia.com/mc/332031.html
https://www.studystack.com/matching-47007
https://www.quia.com/rr/195128.html
https://www.mathwarehouse.com/games/our-games/like-terms-games/matching-action/
http://ia.usu.edu/viewproject.php?project=ia:14344
https://www.khanacademy.org/math/cc-sixth-grade-math/cc-6th-expressions-and-variables/cc-6th-combining-like-terms/e/combining-like-terms-0.5
8th Grade Game Options:
http://www.math-play.com/equation-games.html
https://www.mathgames.com/grade8
http://www.math-play.com/8th-grade-math-games.html
https://www2.gcs.k12.in.us/jpeters/slope.htm
https://www.quia.com/cz/43443.html?AP_rand=162113951
https://www.mathgames.com/skill/8.41-find-the-slope-of-a-graph
https://www.futuristicmath.com/games/6th-grade-square-roots-game.html
https://www.mathplayground.com/ShapeMods/index.html
Additional Math Games:
http://www.sheppardsoftware.com/mathgames/fractions/GreatestCommonFactor.htm
https://www.mathgames.com/skill/6.54-gcf-and-lcm
https://www.mathplayground.com/grade_6_games.html
https://www.mathplayground.com/index_fractions.html
https://www.mathplayground.com/factortrees.html