Each concept will have a link to some BASIC problems you can do. Other study materials are up to you to find. GOOD LUCK :) WE BELIEVE IN YOU!!!
The links to the textbook can be found on the homepage of this website!
http://braingenie.ck12.org/skills/105194
http://braingenie.ck12.org/skills/105195
http://braingenie.ck12.org/skills/105196
http://braingenie.ck12.org/skills/105197
http://braingenie.ck12.org/skills/105200
http://braingenie.ck12.org/skills/105170
http://braingenie.ck12.org/skills/105173
https://www.ixl.com/math/grade-6/write-variable-expressions
https://www.ixl.com/math/grade-6/write-variable-expressions-word-problems
https://www.ixl.com/math/grade-6/evaluate-variable-expressions-with-whole-numbers
https://www.ixl.com/math/grade-6/evaluate-multi-variable-expressions
https://www.ixl.com/math/grade-6/identify-equivalent-expressions
http://www.commoncoresheets.com/Math/Algebra/Applying%20Properties%20of%20Operations/English/1.pdf
http://www.commoncoresheets.com/Math/Algebra/Matching%20Equivalent%20Expressions/English/1.pdf