Question 1052222

I'm  struggling with this word problem:
A 40% saline solution is to be mixed with 60% saline solution to obtain 8 liters of 55% saline solution. How many liters 40% solution should be used?
<pre>Let the amount of 40% saline solution to mix, be F
Then amount of 60% saline solution to mix = 8 - F
We then get: .4F + .6(8 - F) = .55(8)
.4F + 4.8 - .6F = 4.4
.4F - .6F = 4.4 - 4.8
- .2F = - .4
F, or amount of 40% saline solution needed = {{{(- .4)/(- .2)}}} = {{{highlight_green(matrix(1,2, 2, L))}}}