Ascientist has two solutions, which she has labeled solution a and solution

b. each contains salt. she knows that solution a is 65% salt and solution b is 90% salt. she wants to obtain 150 ounces of a mixture that is 85% salt. how many ounces of each solution should she use?

To determine the amount of each solution that she should use, we do mass balance for the whole process. We let x be the amount the 65% salt and y the amount of the 90% salt. We do as follows:

The total mass should be equal to 150 oz.

x + y = 150

Doing a salt balance, we obtain the second equation:
.65x + .90y = 150(.85)

Solving for x and y, we obtain:

x = 30 oz
y = 120 oz