Mathematical communication skills of SMP Negeri 3 Tolitoli students on set operations material in terms of mathematical ability. This type of research is qualitative research. The subjects of this study were selected based on their mathematical abilities. The subject was given a written test with set operations material and then interviewed. This study uses a triangulation method, namely by comparing the results of written tests and interviews. The results of this study are (1) Subjects with high mathematical abilities achieve three indicators of mathematical communication skills in set operations, namely being able to express mathematical ideas through oral and written; able to interpret and evaluate mathematical ideas both orally and in writing; and able to use terms, mathematical symbols to model mathematical situations or problems. ( 2) Subjects with moderate mathematical ability achieved two indicators of mathematical communication skills on set operations, namely being able to express mathematical ideas only through writing, and being able to interpret and evaluate mathematical ideas orally and in writing. (3) Subjects with low mathematical ability achieved one indicator of mathematical communication skills on set operations, namely expressing mathematical ideas in writing.

This study aims to describe the problem solving of FI and FD students in solving social arithmetic problems. Subjects in the study were obtained based on the results of the Group Embedded Figure Test cognitive style test developed by Witkin at SMPN 4 Palu. The results showed that FI subjects were able to: identify what was known and what was asked, make a problem-solving plan and would use the "profit formula" to determine answers, implement a structured problem-solving plan, according to a plan that had been prepared previously and be able to apply knowledge so that they can solve the problem correctly, and check the answers again by using the "purchase price formula". While FD can identify what is known and what is being asked by reading the questions and using the question mark symbol, making a problem-solving plan by first looking for the "remaining and selling price" that is not yet known, then looking for the "overall selling price" by adding up " selling price" that has been obtained and using the "profit formula" to get an answer but still unsure of the formula he will use, using problem-solving strategies according to what is planned, and re-examining the answers by rereading and checking the answers step by step.