<h2>
Explanation:</h2>
Here we have the following expression:

So we need to extend this. Remember that the difference of squares tells us:

So here:

Thus:

Step-by-step explanation:
14. 8
15. 60
16. 42
17. 45
18. 2
19. 8
20. 13
21. 18
Answer:
so you multiply the 13 by 12. Then divid 12 by 2 to get 6 as the radius then use a calculator and type in 2(PIE SYMBOL) R. R=radius then whatever number you get cut it in half then subtract it from 13x12.
You need to state more info, this isn't even a question