Ascientist has two solutions, which she has labeled solution a and solution b. each contains salt. she knows that solution a is 60 % salt and solution b is 85 % salt. she wants to obtain 40 ounces of a mixture that is 65 % salt. how many ounces of each solution should she use?

x = amount of ounces in first substance

y = amount of ounces in second substance

well, we know that substance A has "x" ounces and has 60% of salt, so the total amount of salt in A will just be 60% of "x" or namely 0.60x.

likewise for the substance B, 85% of "y" will just be 0.85y.

we know that if we add those ounces we'll end up with a mixture of 40 ounces, thus x + y = 40, and their combined pure salt amounts will also be 0.6x + 0.85y, so let's proceed.