Given IP  43 . 72 . 153 . 171 / 12  
#1. & 2.  Find the SubNetwork 

#3.  Find the First useable IP address  43 . 64 . 0 . 1 
#4.  Find the Broadcast address  43 . 79 . 255 . 255 
#5  Find the Last useable IP address  43 . 79 . 255 . 254 
#6.  What is the Total Number of IPs per Subnet?  1048576 
#7.  How many useable Hosts address per subnet?  1048574 
#8.  What is the Next Subnet Number?  43 . 80 . 0 . 0 
#9.  What IP Class is this?  Class A 
#10.  How many possible Subnetworks with this class?  Bits this Class = 8 Bits Subnet Mask= 12 2^ 4 = 16 