Answer:
a ≈ 14 or 6
Step-by-step explanation:
264 = π × a × (20 - a)
a(20 - a) =
≈ 84 (rounded off to nearest whole number)
Opening the brackets we get;
a² - 20a + 84 = 0
Applying the quadratic formula we get:
a ≈ 14 or 6
Altitudes make right angles so it is C
Answer:

Step-by-step explanation:
Regan needs the following:
yards for a dress

Total Length of fabric needed

The number of yards of 45-in. fabric needed is 
Answer:
x=9
Step-by-step explanation:
Using elimination method.
Add equation 1 to equation 2
x + y = 11
x - y = 7
---------------
2x + 0 = 18
Divide both sides by 2
2x = 18
---- ----
2 2
x = 9