Answer:
20
Step-by-step explanation:

For long division, you would put 700 in the middle, since the fraction would be 700/21. Then you would figure out how many times 21 goes into 700. Then you would subtract 700 by the amount it would be before it went above 700 by multiplying it by 21. Then, if it is not able to go into 700 fully, you would put a decimal and bring a 0 down.
The 3 is a positive integer and the 7 is a negative integer so you would do "KFC" also known as (Keep, Flip, and Change)
3
("Keep" the 3 positive)
-
("Flip"the minus sign into a plus sign)
-7
("Change" the negative sign into a positive sign)
So therefore, you would have:
3 + 7, which equals 10
The answer is 60 ft
You do L × W ×H
which is 3 × 4 × 5 = 60