Khan Academy -- https://www.khanacademy.org/  -- When you have a question between tutoring sessions, Khan Academy is the best place I know to figure out how to do something. You can search for a very specific concept and there's a high probability he will have a video explaining how to do it and showing an example.  

Algebra 1 formula sheet -- https://www.gadoe.org/Curriculum-Instruction-and-Assessment/Assessment/Documents/Milestones/EOC-Resources/Alg_1_Formula_Sheet.pdf

Geometry formula sheet -- https://www.lcps.org/cms/lib/VA01000195/Centricity/domain/732/sol_resources/SOLformulas.pdf

Algebra 2 formula sheet -- https://www.rcboe.org/cms/lib/GA01903614/Centricity/Domain/9559/Algebra_2_Formula_Sheet.pdf

Trig Identities -- https://sciencenotes.org/wp-content/uploads/2017/09/TrigIdentities.pdf

Common Core High School Math Reference Sheet -- https://www.nysed.gov/sites/default/files/programs/state-assessment/public-facing-reference-sheet.pdf

Properties of Exponents and Logs -- https://wou.edu/mathcenter/files/2015/09/Exponents-and-Logarithms.pdf