Static Routing : It means we are installin routes in routing table of router manaully.

Syntax :  (config)# ip route network_id subnet_mask  next_hop_ip/Subnet mask

On Serial Link : Exit_interface is used

On Ethernet Link : Next_hop_Ip is used.

Task: 

I had done static routes on R1 and R2 for network of 20 and 10 because with R1 bydefault network of 10 and 12 is connected so to reach network of 20 we have to give static route .similar with R2