We are given this

write it as the difference of cubes

use the formula for the difference of cubes

Now use the formula for the difference of squares as 

The cube root of 81 is 4.32674871092
Answer:
7 Miles is the answer.
Step-by-step explanation:
10*7=70.
Answer:
87 feet
Step-by-step explanation:
Two of the sides here are unknown. The one on the leftmost side is equal to 9, since on the other side it also has a length of 9 feet. The section on the top right has a length of 30-9-9=12 units. Adding all of these values together now, you get a total perimeter of:
30+9+12+9+9+9+9=87 feet
Hope this helps!