In this math lesson, the instructor reviews the concepts of addition and subtraction, demonstrating how they are inverse operations through examples, such as writing subtraction sentences for given numbers and finding missing values in addition statements. The lesson then transitions to a new topic on time, emphasizing the importance of clocks in daily life and introducing key time-related vocabulary, including terms like analog clock, hour hand, and minute hand. Students are encouraged to familiarize themselves with these concepts using a guard clock or a paper printout and participate in activities like singing to learn about reading time.