The sides
12-3a
12-3a
4(2a-5)=8a-40
so for perimeter we + them
(12-3a)+(12-3a)+(8a-40)
=
2a-16
If the center is at (0, 0) and the vertex is at (20, 0), then the distance, a, is the length from the center to the vertex, 20. The distance from the center to the focus is c. The distance from the center to the focus is 16, so c = 16. The formula we use to find the focus is

. We have our c value and our a value, so we will sub in those to find b.

and 256 = 400 - b^2. -b^2 = -144, so b = 12. There you go!
The answer is c because if you have 9 legos and your friends gives you 10 You have now 19 legos
5p = 80b
3(5p) = (80b)3
15p = 240b
Lan need 240g of butter to make fish pie for 15 people.