9 gal=amount of water to be added with 0% concentration of sugar
x=gal of 40% sugar solution
23%=final solution
(9gal)(0)+(x)(40%)=23%(x+9gal)
0+(x)(40%)=23%(x+9gal)
0+(x)(40%)=23%(x) (23%)(+9gal)
(x)(40%)=23%(x) + (207%gal)
(x)(40%)23%x=23%(x)23%x + (207%gal)
17%x=207%gal
17%x/17%=207%gal/17%
x=12.18gal
