I got 6 for my answer, but I'm not 100% sure if I'm right.
6(2x-11)+15=21
12x-66+15=21
12x-51=21
+51 +51
12x=72
----- ----
12 12
x=6
Her first rate was faster. The 10 minutes with a change in elevation of -200ft.
In order to solve this you need to have the same minutes. In this problem, I just simply took the 10 minutes and the -200ft and doubled it. Now both rates have 20 minutes. The first rate would have gone -400ft in 20 minutes while the second rate was only -300ft in 20 minutes. I hope this wasn't confusing, and I'm willing to explain more.
The area of the disk is approximately 314 inches
The rule is that if multiplying with powers you will add the m power to the n power and then that will be your answer .
