Indigenous people of Dayak tribe in Kalimantan, Indonesia have traditionally relied on a system of mutual cooperation called "handep." The cultural context has an influence on students mathematics learning. The "handep" system might be suitable for modern learning situations to develop mathematical problem-solving skill. The objective of the study was to investigate the effect of "handep" cooperative learning model compared to problem-based learning model on mathematical problem-solving skill of rational exponent material. The research was conducted through pretest-posttest non-equivalent control group design. The sample of 66 students was selected from the population of 304 students through cluster random sampling. The mathematical problem-solving skill assessed with essay test of the open-ended question had reliability coefficient of r[subscript xx'] = 0,71. The students' answers scorings were obtained with the rubric of mathematical problem-solving skill. Data analysis is conducted through ANACOVA. The result presents that the mathematical problem-solving skill of students who learned through "handep" cooperative learning model is better than problem-based learning. "Handep" cooperative learning model is suitable to enhance the mathematical problem solving skill of students in Kalimantan-Indonesia cultural context. The teacher should construct the instructional material use metacognition questioning strategy and also be familiar to their students' prior knowledge of mathematics.