We know that the total volume of the solution is 187 cubic feet.
187=3x+8x
187=11x
17=x
Now we know that the ratio 3 to 8 is 51 to 136.
Double check, (3*17)+(8*17)=187.
I'm not sure which part of the ratio is water, but knowing this information, you should be able to solve it. I believe it may be this:
The total volume of milk is 51. If the rest of the solution is water, then 187-51=136.
