As the given IP belongs to network of class C we know that out of 32 bits the first 24 bits are reserved for the nid . The subnet mask given to us is 255.255.255.224.
The last octet in this gives us the information about the subnet id bits i.e 3 as 224=11100000
So they are asking for the decimal value of the last octet of the last host of the 6th subnet ... So SID =110 As it is the last host rest all bits are 11110(last bit is not one because if it was 1 then it becomes directed broadcast address)
So we get 1101 1110=128+64+16+8+4+2=222.
Note: They are referring to subnet with id =6 if 6th subnet would be there then id would be 101 and ans will be 190 as
000- 1st subnet 001=2nd subnet 010- 3rd subnet 011-4th subnet 100-5th subnet 101-6th subnet 110-7th subnet 111-8thsubnet