From one IP to send a packet to another?

Question

Network routing

From IP A, you need to send a packet to IP B if
IP A, IP B, MAC A, IP R are known

Please answer these questions, I don't understand

1. How to see if A and B are in the same network?
   
2. How to find out from a MAC R router?
   
3. How does the router know who to send the packet to if only IP B is known?
   

Answer 1

Static Routing

Answer 2

1) A and B are in different networks, this is indicated by the fact that they are in different vlans.
2) the question is not entirely clear. who owns R?
3) sends arp request("who has ip address B here")

Answer 3

1. Apply a bitwise "AND" to the subnet mask and IP A, and to the subnet mask and IP B; compare result. If the result is the same - A and B are in the same network.
2. Send a broadcast ARP request to the network with the appropriate question.
3. You only know IP B, and the router knows its routing table, which it uses when resolving such issues.