You can't get either the gateway address or the subnet mask, just by looking at the IP address. The default gateway is often the first or the last usable IP address in a subnet, but this doesn't need...
You cannot find the gateway address just by looking at the IP address and the subnet mask. You need to interrogate the system by using the appropriate TCP/IP utility.
If you are using Windows XP or 2000, click start button then on "run"
Enter cmd and pre enter
Type ipconfig and press enter. If you need more info type ipconfig /all and press enter.
If you are...