Algebra: Creating Equations Remix
This site from Khan Academy teaches High Schoolers how to create equations through a series of 298 questions and interactive activities aligned to 5 Common Core mathematics skills. https://www.khanacademy.org/commoncore/grade-HSA-A-CED
Practice questions include word problems, systems of equations, and inequalities. I would encourage students to use Desmos graphing calculator (https://www.desmos.com/testing/virginia/graphing) to help answer the questions or check solutions graphically.