ElectricPavlov

You have two sides   and the total of the THREE sides....just subtract the two sides from the total to find the remaining side length.

21 - 9 - 5 = 7" = AC

1800 miles  /  300 miles/day  = 6 days

Because 6% = 6/100 = .06    

   I added 4 instead of r   because that is what your posted question asked. 

Cirle formula  

    (x-h)^2   + (y-k)^2 = r^2       center = h,k

                   ( x+5)^2 + (y-2)^2 =r^2

                   x^2 + 10x   + 25   + y^2 -4y   + 4 = r^2

                  x^2  + y^2 + 10x -4y  = r^2 -29                 Multiply both sides by 2 to get the 2y^2

                 2 x^2 + 2y^2 + 20x - 8y = 2r^2 - 58         and 2^r^2 - 58 = 40     2r^2 = 98   r^2 = 49     r= 7

A+B + C +4 = 2 + 20 + (-8) + 4  = 18

IF you meant    A+B+C+r     then  =   2+20+(-8) +  7 = 21

6% x = .48

x = .48/.06 = 8.00       Price = $ 8 

deleted

That's what I did originally, but you can use the same color twice.....just not next to itself.....which adds 12 mre possibilities.

Wondering if it wouldn't be     4 choices for first color   3 choices for second color  3 choices for third color = 36 possibles.

  I come up with 11 if you count ABCD  (don't forget the diagonals)....and wondering...if you use three of the vertices, then isn't it the same square ABCD.....if yes, AND you can't use ABCD, then I get only 6.

rwb

rbw

rgw

rwg

rgb

rbg

rwr

rbr

rgr

wbg

wgb

wbr

wrb

wgr

wrg

wrw

wgw

wbw

etc for the other two colors.....    

9 x 4 = 36   is what I find 

  ( I added the two stripes of same color but not NEXT to each other).....Anyone else?