Students will learn how to add and subtract fractions with different denominators by finding a common denominator. It is important to find a common denominator so you can understand the relationship between the fractions and perform the arithmetic accurately. The document provides examples of adding and subtracting fractions with different denominators, as well as evaluating expressions with fractions. Real-life examples where adding and subtracting fractions is useful are also given, such as finding perimeter, cooking, carpentry, and calculating gas amounts.