Two 20.0-mL samples, one 0.200 M KOH and the other 0.200 M CH3NH2, are titrated with 0.100 M HI. What is the volume of added acid at the equivalence point for each titration

The volume of the added acid at the equivalence point in case when titration is done with KOH is,  

VHI * MHI = VKOH * MKOH

VHI = 20.ml * 0.200 M / 0.100 M

VHI = 40.0 ml

The volume of the added acid at the equivalence point in case when titration is done with CH3NH2 is,  

VHI * MHI = VCH3NH2 * MCH3NH2

VHI = 20.0 ml * 0.200 M / 0.100 M = 40.0 ml

As HI is the strong acid and KOH is the strong base, therefore, the pH will be neutral at the equivalence point.  

On the other hand, as HI is the strong acid and CH3NH2 is the weak base, therefore, pH will be acidic at the equivalence point.