CCNAs are expected to be able to understand subnetting - here's how to do the calculations in your head:
If you have an IP address of 195.168.1.18 and subnet mask of 255.255.255.192, and you want to know how many networks you have, what the range of addresses is and the broadcast address for each network, do the following:
Take the 192 (last octet in the subnet mask) and subtract it from 256 resulting in a value of 64. This is the "key" value on which everything revolves.
The first network will be 195.168.1.0, the second will be 195.168.1.64, the third will be 195.168.1.128, and the fourth network will be 195.168.1.192 (note how all we're doing is adding the 64 from the earlier calculation each time). It also means that a subnet of 255.255.255.192 gives you four networks.
Given that information, we now need to determine what the broadcast address is for each network. It's simple: It's the network address of the next network minus 1. So, with our first 195.168.1.0 network, the broadcast is 195.168.1.63. (The second is 195.168.1.127, the third is 195.168.1.191 and the fourth is 195.168.1.255).
All we need to do now is work out what the valid hosts are. That's simple. It's what's between the network address and the broadcast address. So the first network is 195.168.1.1 to 195.168.1.62, the second is 195.168.1.65 to 195.168.1.126, the third is 195.168.1.129 to 195.168.1.190 and the fourth is 195.168.1.193 to 195.168.1.254.
We now have all the information we need to say that the original address (see above) of 195.168.1.18 has a network address of 195.168.1.0, a broadcast address of 195.168.1.63 and is part of a range 195.168.1.1 to 195.168.1.62.
Make sense? That's what happens when you subnet a class C network. Subnetting a class B is pretty similar. If you can follow the above, and learn it, then you'll be away.