Answer:
The correct answer is A. 167 milliliters of 7% solution and 333 milliliters of 4% solution and here is how:
If x is the number of milliliters of the 7% saline solution and y is the number of milliliters of the 4% saline solution then add up to 500 milliliters total, so x + y = 500.
and if we do
x + y = 500
x = 500 - y
0.07x + 0.04y = 25 (substitute 500 - y for x)
0.07(500 - y) + 0.04y = 25
35 - 0.07y + 0.04y = 25
-0.03y + 35 = 25
-0.03y = -10
y = 333.333...
y = about 333
x = 500 - y = 500 - 333 = 167
Then you know why the answer is A.
Step-by-step explanation:
