This math topic focuses on the skill of finding the lowest common denominator to subtract fractions. Each problem presents pairs of fractions, and students must identify the smallest common denominator that would allow them to perform the subtraction operation. The level is introductory, targeting basic understanding of fraction subtraction by adjusting one of the denominators, as part of a larger unit on introductory fraction addition and subtraction. Each question lists multiple-choice answers for students to select the correct lowest common denominator.