To perform addition and subtraction of fractions, one must find what?

The process of adding and subtracting fractions requires finding the lowest common denominator (LCD) because it allows you to express each fraction with a common base. This is essential because fractions with different denominators cannot be directly added or subtracted.

By identifying the lowest common denominator, you can convert each fraction to an equivalent fraction that has the same denominator. This uniformity makes it possible to combine the numerators while keeping the denominator constant. After performing the operation, the resulting fraction may then need to be simplified, if applicable.

Other choices, while related to fractions and their manipulation, do not facilitate the addition and subtraction process directly. For instance, the greatest common factor and highest common multiple are useful in other contexts, such as simplifying fractions or finding least common multiples for grouping, but they do not specifically aid in the addition and subtraction of fractions. Similarly, averaging the denominators does not provide a suitable base for performing these operations. Thus, identifying the lowest common denominator is fundamental to accurately and efficiently handling fraction addition and subtraction.