Subnet #1 has 192.168.135.67/28 host
Subnet #2 has 192.168.135.90/28 host
and
Subnet #3 has 192.168.135.102/28 host
Any available host address within the network is valid for a router interface address. A router is just another host on the network, albeit the one to which traffic destined for a different network is sent. A router interface can be assigned any valid host address. Most people assign either the first or last usable address to the router interface, but that is not a requirement. It helps to be consistent.