This math topic focuses on calculating the dimensions of rectangles on a Cartesian grid, specifically dealing with problems that involve determining missing widths or heights given the area of the rectangle and the measurement of one of its sides. The problems involve using the formula for the area of a rectangle (area = width × height) to find the missing dimension when only one dimension and the area are known. All scenarios presented are confined to positive values only. This set of problems helps to reinforce the basic concepts of geometry and algebra within the context of a Cartesian grid.