This is "Ctrl + C & V" version of @Ashwin Kulkarni Answer.
I feel there should be a correction. (find as marked blue)
Subnet ID = 199.166.15.112.
4 bits are used for subnetting, hence 0000,0001,0010...1111 are the subnets
First usable host of the first subnet = 199.166.15.0000 0001 = 199.166.15.1
Last usable host of the first subnet = 199.166.15.0000 1111 = 199.168.15.15 should be 199.166.15.0000 1110 = 199.168.15.14
Last usable host of the whole subnet = 199.168.15.1111 1110 = 199.168.15.254
Third host of the 1st subnet = 199.168.15.0000 0011 = 199.166.15.3