Answer:
subnet : 16
host per subnet : 4094
Explanation :
172.18.0.0 is a class B type of network.
so you must take the 2 last octet in the subnet mask.
so that you change the subnet mask into the binary,
x.x.255.240 / x.x.11111111.11110000
subnets
= 2^x (x is the number of binary numbers 0)
= 2^4
= 16
hosts per subnet
= 2^y - 2 (y is the number of binary numbers 1)
= 2^12 - 2
= 4094