Figure 1 shows four routers with different host requirements.  Each router is connected to the adjacent router with a WAN link.  This shows a need for seven subnets. Figure 2 shows that by borrowing three host bits from a slash twenty four, we can create 8 subnets.  These subnets will be a slash twenty seven. Figure 3 shows that with the remaining five bits we will have 30 valid hosts on each of the subnets.