Khan Academy: https://www.khanacademy.org/math/cc-1st-grade-math/cc-1st-add-subtract

Kahoot: https://embed.kahoot.it/3f81b55b-8bc0-43de-a058-121c557e7c01

Addition within 20  free printable worksheet: https://www.education.com/worksheet/article/addition-to-20-check-in/ 

Free Printable Number sentence Practice sheet: https://www.education.com/worksheet/article/superstar-addition-first/