Question 793912
suppose that one cocktail is 25% ethanol and another cocktail is 110% ethanol.
 How many milliliters of each solution should be mixed to make 10.5 milliliters of an 80% ethanol solution? 
:
I think you are on the right track here, but you can't have 110% ethanol, 100%
is all ethenol, lets say it is 100%
:
.25x + 1(10.5-x) = .80(10.5)
.25x - 1x + 10.5 = 8.4
-.75x = 8.4 - 10.5
-.75x = -2.1
x = -2.1/-.75
x = +2.8 milliliters of the 25% ethanol
and
10.5 - 2.8 = 7.7 milliliters of 100% ethanol
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;
You can confirm this
.25(2.8) + 1(7.7) = .8(10.5)