Hey there!
The 1s in the mask indicate bits that identify the network number, thus one merely need use a bitwise AND operation to extract the network number:
address 10111110.11101001.00011011.00001101 190.233.27.13
mask 11111111 11111111 00000000 00000000 255.255.0.0
(AND) ----------------------------------- -------------
network 10111110.11101001.00000000.00000000 190.233.0.0
so the network address is: 190.233.0.0
Happy learning!