You do it manually by writing out the addresses in binary. Here's how
195.3.4.136 = 11000011.00000011.00000100.10001000
255.255.255.224 = 11111111.11111111.11111111.11100000
You "AND" them to get the network address which is:
195.3.4.128 = 11000011.00000011.00000100.10000000
the broadcast will be the network address with all 1's at the end of the last octet (in this case the last 5 digits since you borrowed the first three of the last octet for the subnet) so it's:
11000011.00000011.00000100.10011111 which is
195.3.4.159 in decimal. Remember, the first three digits, 100, of the last octet are part of the network identifier, the broadcast is the network identifier plus all 1's at the end.
My explanation probably sux but that's how you do it