Ascientist has saline solutions with concentrations of 4% and 14% . he wants to mix some of each solution to get 65 milliliters of solution with a 6% concentration. how many milliliter of each solution does he need to mix together?

Let volume of 4% solution = x and of 14% be y

them x + y = 65(1)    also  using the actual weights of  salt:-

0.04x + 0.14y  =  65*0.06 = 3.9

multiplying the above equation by  -25 we have

-x - 3.5y = -97.5    adding this to equation (1)

--2.5y = -32.5
y= 13 

and x = 65 - 13 = 52

so we need 13 mls of the 14%,  and 52 mls of the 4% solution.