Ok first thing to note is that it says the workstations are connected via a "straight through" cable which is wrong you need a cross over cable if you are connecting two station directly.
Secondly about calculation :-
this is a class C ip address and the subnet mask is also of class C so all the changes will be in the last octet of this address now that being cleared.
/28 = 16 - 2 hosts in each subnet
/25 = 128 - 2 hosts in each subnet
So with a subnet mask of /25 you get both workstations in the same subnet and they will be able to communicate. Basically if you know subneting then this aint a difficult question.
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