Final answer:
To find out how much of the 20% saline solution should be used, set up an equation using the concept of concentration and solve for x.
Step-by-step explanation:
To find out how much of the 20% saline solution should be used, we can set up an equation using the concept of concentration:
(60 cc)(0.70) + (x)(0.20) = (60 + x)(0.25)
Where x represents the amount of the 20% saline solution to be used.
Simplifying the equation:
42 + 0.20x = 15 + 0.25x
0.05x = 27
x = 540 cc
Therefore, the nurse should use 540 cc of the 20% saline solution.