V sol otet = 180 ml , ro= p = ms / Vs
=> ms1 = pxVs = 0,95x180 = 171 g sol initiala otet
c%1 = 9% , c% = mdx100/ms
=> md = msxc%/100 = 9x171/100 = 15,39 g acid acetic
ms.final = ms1 + m.apa (a)
c%.final = 4%
=> 4 = 15,39x100/(ms1 + a)
=> 4ms1 + 4a = 1539 = 4x171 + 4a = 1539
=> a = 213,75 g apa adaugata