Explanation:
To determine how many quarts of each type of bleach to mix to make 8 quarts of 85% bleach, we can set up a system of two equations. Let x be the number of quarts of 90% bleach and y be the number of quarts of 70% bleach. Then:
x + y = 8 (total volume of bleach)
0.9x + 0.7y = 0.85(8) (total amount of active ingredient)
Simplifying the second equation, we get:
0.9x + 0.7y = 6.8
We can then solve for y in the first equation:
y = 8 - x
Substituting this into the second equation, we get:
0.9x + 0.7(8 - x) = 6.8
Simplifying and solving for x, we get:
0.2x = 2
x = 10
Substituting this value back into the equation for y, we get:
y = 8 - x
y = 8 - 10
y = -2
Since we cannot have negative quarts of bleach, this solution is not possible. Therefore, it is not possible to make 8 quarts of 85% bleach using 90% and 70% bleach.