This study aims to find a pattern of correcting mathematical understanding errors in solving mathematical problems for junior high school students. The method used in this research is qualitative. Data collection using triangulation technique: observation, test results, and interviews. Interviews were conducted on three subjects for one month at MTs. The instrument used is a mathematical problem-solving test. This study found patterns of improvement in mathematical problems in geometry, namely the area and perimeter of rectangles and lines. This study found that the pattern of mathematical understanding errors can be corrected by applying patterns such as reminding the material of rectangular shapes, parallelograms, algebraic forms, and units of measure, writing down everything that is known in the problem, and making an example of a variable if it cannot be written directly. The pattern of improving mathematical understanding can solve the mathematics problems of junior high school students. Furthermore, this pattern of mathematical understanding errors can be applied by teachers to improve math problems and embed geometric concepts in mathematics learning.