Static routing how to subnet at least 50 host?

Your Question means how many subnets we can have with atleast 50 hosts in each Subnets

for, Class A  IP

Block Length/Size = 64 in 4th Octet,

Subnet ID/Borrowed Bits = 18 

So total no. of Subnets = 2^18= 262144

for, Class B  IP

Block Length/Size = 64 in 4th Octet,

Subnet ID/Borrowed Bits = 10

So total no. of Subnets = 2^10= 1024

for, Class C  IP

Block Length/Size = 64 in 4th Octet,

Subnet ID/Borrowed Bits = 2

So total no. of Subnets = 2^2= 4

Thanks