A book about calculating junior high school mathematics
Junior high school mathematics includes rational numbers, algebraic expressions, fractions, equations (groups), inequalities, triangles, quadrilaterals, pythagorean theorems, circles, similarities, congruences, axisymmetries, central symmetry, simple trigonometric functions, preliminary probabilities, quadratic roots and so on. It's simpler. Just buy a junior high school math basic knowledge and review it once.