chem
posted by help!!! .
How many milliliters of a 15.0%, by mass solution of {KOH}(aq) (d = 1.14 g/mL) are required to produce 25.0 L of a solution with pH = 11.60?

Calculate molarity of KOH solution.
That is 1.14 g/mL x 1000 mL x 0.15 = approximately 175 grams KOH. So mols KOH = 175/56 = about 3 M.
Now go to what you want to prepare. You want pH = 11.60 which is pOH or 2.40 or (OH^) = about 0.004 M.
Now mL(soln 1) x M(soln 1) = mL(soln 2) x M(soln 2)
You need to redo the whole problem because I estimated molar masses and rounded here and there to make it quicker to calculate. The answer is approximate only so you need to put in the exact values. 
thanks alot !! =)