Answer:
You should add 4 fluid ounces of 50% strength tea
Explanation:
The actual fuction that gives the final concentration should be:
y=[(6)(1.0)+x(0.5)]/(6+x)
Probably it was a typing problem (a missing slash to indicate division). With the function given, the problem has no solution.
We want the strength of the iced tea to be at 80%.
So, to find how many fluid ounces of 50% strength tea (valor of x) you should add, we just need to use the equation of the final concentration with the value of y = 0.8 (y is the concentration of the tea after adding x fluid ounces of 50% strength tea):
0.8 = (6*1 + x*0.5) / (6+x)
0.8 * (6+x) = 6 + 0.5x
4.8 + 0.8x = 6 + 0.5x
0.3x = 1.2
x = 4 fluid ounces