Mathematical word problems are the most common form of mathematics problem solving implemented in K-12 schools. Identifying key words is a frequent strategy taught in classrooms in which students struggle with problem solving and show low success rates in mathematics. Researchers show that using the concrete-representational-abstract (CRA) sequence with explicit instruction improves students' computational skills. Researchers also show that schema-based instruction increases students' problem-solving performance. This study combined CRA and schema-based instruction for three students receiving tertiary interventions for mathematics instruction. A functional relation was found for the three students' problem-solving performance. The researchers also interviewed each student to gain a more complete picture of students' thinking. Results and implications are discussed.