Maybe this question has been answered a million times, but I can't find one that fits my requirement exactly.

I am using Windows 7 with ip address of 145.x.x.x host in my workplace. I have a guest with Linux Mint on vmware with 20.x.x.x ip address in network bridge mode. The host pc connects to my office LAN and several sites over WAN connectivity and the guest is connected to Internet directly.

I would like to configure the guest os network as I can use the internet and as well as can access my office LAN and also other sites connected with 145.x.x.x subnets from the guest OS.

I have tried with IP alias from the guest OS, but using IP alias it can only access 145.17.x.x network which is the only LAN I am connected to but it cannot connect to other subnets.

Is it possible to connect the guest OS to access both subnets so that It can use internet from 203.x.x.x and access office LAN and WAN sites using 145.x.x.x?

You need to set up NAT on the host system. Either that or login to every other computer on the internet and add a static route for 20.x.x.x to go to 145.x.x.x

Not sure if this applicable to you, but if your Windows Machine is connecting via 2 NICs you should be able to add another one to your virtula machine and bridge that to the second on your Win 7 box.
I have 2 NICs on this box, one is connected internally the other connected externally. A windows VM connects via bridging to the internal network, this box (Linux) connects externally.
I can and have connected my main linux box to both networks directly through the two cards but it is preferred to not do that. And likewise, I can connect my Windows 7 VM to both. Done through bridged adapters. One is a 198.x.x.x network and the other a 10.x.x.x network.