This lecture is about number operations of addition and subtraction. Students learn how to add and subtract numbers from one-digit up to three-digit, both with and without carrying or borrowing. Addition means putting things together to find the total, while subtraction means taking away to find what is left or the difference. The lecture includes simple examples, word problems, and real-life situations like counting books, students, or items sold. It also teaches how to solve problems step by step using place values (ones, tens, hundreds) and how to carry or borrow when needed. By the end, students can easily add and subtract numbers and apply these skills in everyday life.