Final answer:
The sum of the lengths 6 feet 10 inches and 8 feet 9 inches is 15 feet 7 inches, after converting and adding the inches separately and then adding that to the total feet.
Step-by-step explanation:
To find the sum of 6 feet 10 inches and 8 feet 9 inches, we can add the feet together and the inches together separately. First, we add the feet: 6 ft + 8 ft = 14 ft. Next, we add the inches: 10 in + 9 in = 19 in. Since there are 12 inches in a foot, we can convert 19 inches into feet and inches. This gives us 1 ft 7 in.
Now, add this to the original sum of the feet:
14 ft + 1 ft = 15 ft
So, we have 15 ft and we still have the leftover 7 inches. Thus, the total sum is 15 feet 7 inches.