Summary: The text provides an in-depth analysis of solid geometry and co-ordinate geometry in three dimensions, specifically focusing on various mathematical concepts such as volume calculations of tetrahedron, skew lines, transformations of coordinates, spheres, cones, and central conicoids. The author, Prof. M. L. Khanna, provides comprehensive theory, fully solved questions, and formulas for various university papers and competitive examinations. Chapter VII covers the volume of a tetrahedron, skew lines, and transformations of coordinates, while Chapter VIII delves into the sphere, its various forms, and tangent planes. Moreover, the text discusses the cone, central conicoids, the plane section of a sphere, and the orthogonal intersection of two spheres. Essential formulas, calculations, and proofs for shaping mathematical acumen are provided to enhance the understanding of solid geometry principles and applications. Overall, the book serves as a valuable resource for students preparing for higher-level mathematics examinations covering diverse topics of solid and co-ordinate geometry.