how do you answer this?
tod wants to make a 12fl. oz of a 20% sugar solution by mixing together a 50% sugar solution and a 10% sugar solution. how much of each solution must he use?

Question

anonymous · Answer

12 ounces at 20 percent means you want 20% of 12 = 2.4 ounces of sugar.  
if you put in x ounces of 50% solution it will have .5x sugar and you will then add 12 -x of 10% sugar giving .1(12-x) sugar.  all together you will have 
$$.5x+.10(12-x)$$ sugar and you want that to be 2.4 so solve 
$$.5x+.1(12-x)=2.4$$ for x

anonymous · Answer

i would first multiply by ten to get rid of annoying decimals and write 
$$5x+(12-x)=24$$
$$4x+12=24$$
$$4x=12$$
$$x=3$$

anonymous · Answer

Recall that x is the amount of the 50% solution and (12 - x), in this case 9, is the amount of 10% solution.

anonymous · Answer

where does the 12-x come from

anonymous · Answer

If you add x Oz of one fluid and want to fill a 12 Oz container, you need the difference between 12 and x, e.g. (12-x), Oz of the other fluid.

anonymous · Answer

oh ok thanks

anonymous · Answer

ok i still dont get it

anonymous · Answer

what part?

anonymous · Answer

where the 12-x comes from i dont know if im doing right but i have an equation that looks like this .5x+.2x=3.6 and i dont know where to go from that

anonymous · Answer

i mean .5x+.1x=2.4

anonymous · Answer

was that provided to you or did you come up with that?  because that would assume that you are adding equal amounts of each solution., which is not the case.