This document provides instructions for finding the prime factors of numbers and calculating the greatest common factor (GCF). It explains that to find the GCF of two numbers, one should first prime factorize both numbers, write out the prime factorizations, and then multiply the common factors. Examples are given of prime factorizing 144, 225, and 400, and key terms like common factor and greatest common factor are defined. Instructions are provided for a three step process to calculate the GCF by prime factorizing both numbers and multiplying their common factors.