Students who have difficulty with mathematics may have trouble understanding underlying concepts of numbers and operations. The concrete-representational-abstract (CRA) instructional sequence of instruction provides a way for teachers to help students gain meaning from numbers and the mathematical concepts those numbers represent. This study addresses evidence-based practices and applies CRA methods to instruction address concepts such as rounding, regrouping, and equivalent fractions. The purpose of this study was to investigate the effects of CRA instruction on the performance of elementary students across varied areas of need related to poor conceptual understanding and proficiency in completing tasks related to numbers and operations. The researchers implemented a multiple baseline across behaviors design for two students who were at risk for mathematics failure. A functional relation was found for CRA intervention and rounding, regrouping, and fraction concepts for the two students. Results and implications are discussed.