If you are struggling to teach a math concept to a student, it may be helpful to know that according to research, when learning mathematics, all children have the same learning trajectory and must learn some concepts before they can learn others. For example, children learn how to match numbers of objects before they know what the numbers are called.
See AltShift.education for a professional development module called “Learning Trajectories Approach to Help All Students Progress in Math.” It includes downloads of the trajectories themselves as well as trajectory assessment planning worksheets.