A = nuts of $2/lb
B = nuts of $7/lb
let's say we'll mix "x" lbs of B to get a mixture with A of "y" lbs, therefore

30?
30pi = 2pi r
30pi / 2pi = 15
15 = r
double the radius to get the diameter
15)2 =30
Well, I know to find the mean you add all the numbers and divide it by how many numbers there were, so I'm guessing you just do that with the stem and leaf plot. I hoped this helped a bit
6. m=2
7. m=3
8. m=0
Hope it help