This math topic focuses on practicing fraction subtraction with a missing value in mixed numbers. Specifically, problems require solving for an unknown fraction in subtraction equations where one denominator has been changed. The topic is part of a larger introductory unit on mixed number addition and subtraction. Each problem provides a subtraction equation and a set of answer choices, with one correct fraction that brings balance to the equation, enhancing skills in manipulating and understanding fractions within nonlinear equations.