How many mL of a solution of NaOH with pH equal to 1.395 x 101 do you need to mix with pure water to obtain 399 mL of a final solution with pH equal to 9.066 ?

pH 13.95; convert to H^+ by

pH = -log(H^+) and change to OH.
Then convert pH 9.066 to OH^- the same way.
mLsoln1 x Msoln1 = mLsoln2 x Msoln2.