Recall n = c *(v/1000) if the volume is in Cm3.
Now, n(HCl)= 0.2 x (25.0/1000)
n(HCl) = 5x10-3
Since the relationship stoichiometrically is 1:1 (H+:OH-), we can infer that
n(NaOH) = 5x10-3
and by rearranging to c=n/(v/1000)
c(NaOH) = (5x10-3) / (21.5/1000)
c(NaOH) = 10/43 moldm-3 and to 3dp, c(NaOH) = 0.233moldm-3