Understand Routing: IPsec?

Question

FreeBSD

Good afternoon!
I describe the situation:
there is locale A: 192.168.75.0/24
its main gateway is 192.168.75.225
locale A has access to the Internet. (WAN, white IP)
there is locale B: 192.168.51.0/24
its main gateway is 192.168.51.225
locale B does not have Internet access, there is only access to locale A. (WAN, gray IP 10.xxx)
On the main local gateways networks installed pfSense 2.0. The networks are connected using an IPsec tunnel.
Result: network B is pinged from network A and network A is pinged from network B.
So, the question itself is:
Purpose: There must be Internet in LAN B. It should receive it from local A. The
question is how to register routing in networks and does IPsec tunnels allow to implement the given one?

Answer 1

Did you yourself read what you wrote?

locale B does not have access to the Internet, there is only access to locale A

and than

LAN A must have internet. She should receive it from locale B.

Describe everything so that it is clear.

Answer 2

a better diagram

Answer 3

On computers in local B, you assign the router of local A as
a gateway.

Answer 4

Or you can do it in a crooked way, for example, in the main office there is an Internet (Network A), but in others there is not (Network B), but there is a grid to the main one, basically there is a proxy (SQUID), and where something is needed on remote servers then download from the Internet, then simply specify the proxy in grid A, and it already replaces the address, proxies the traffic and releases it to the Internet.