50ml = 50cm³ = 0,05dm³
C = n/V
n = 0,15 mol/dm³ × 0,05dm³
n = 0,0075 mol CH₃COOH
..............................
CH₃COOH + NaOH ----> CH₃COONa + H₂O
1 mol...............1 mol
1 mol CH₃COOH ------------1 mol NaOH
0,0075 mol CH₃COOH --- X
X = 0,0075 mol NaOH
V = n/C
V = 0,0075/0,1
V = 0,075 dm³ = 75cm³ = 75 mL