Final answer:
To find the least common denominator (LCD) of fractions, you need to find the smallest number that both denominators can divide into evenly. In this case, the LCD of 4/7 and 2/3 is 21.
Step-by-step explanation:
To find the least common denominator (LCD) of the fractions 4/7 and 2/3, we need to find the smallest number that both 7 and 3 can divide into evenly. One way to find the LCD is to list the multiples of both 7 and 3 and look for the first common multiple. The multiples of 7 are 7, 14, 21, 28, 35, and so on. The multiples of 3 are 3, 6, 9, 12, 15, 18, 21, and so on. The first common multiple is 21. Therefore, the least common denominator of 4/7 and 2/3 is 21 (option A).