updated README.md on subnet mask definition and example
diff --git a/README.md b/README.md
index f706bb5e1..80484e09c 100644
--- a/README.md
+++ b/README.md
@@ -144,27 +144,10 @@ An Internet Protocol address (IP address) is a numerical label assigned to each
 <details>
 <summary>Explain subnet mask and given an example</summary><br><b>
 
-A Subnet mask is a 32-bit number that masks an IP address, and divides the IP address into network address and host address. Subnet Mask is made by setting network bits to all "1"s and setting host bits to all "0"s. Within a given network, two host addresses are reserved for special purpose, and cannot be assigned to hosts. The "0" address is assigned a network address and "255" is assigned to a broadcast address, and they cannot be assigned to hosts.
+A Subnet mask is a 32-bit number that masks an IP address, and divides the IP address into network address and host address. Subnet Mask is made by setting network bits to all "1"s and setting host bits to all "0"s. Within a given network, out of the total usable host addresses, two are always reserved for specific purposes and cannot be allocated to any host. These are the first address, which is reserved as a network address (a.k.a network ID) and the last address used for network broadcast.
 
-**For Example**
+[Example](https://github.com/philemonnwanne/o0o0o/tree/main/exes/exe-09)
 
-```
-| Address Class | No of Network Bits | No of Host Bits | Subnet mask     | CIDR notation |
-| ------------- | ------------------ | --------------- | --------------- | ------------- |
-| A             | 8                  | 24              | 255.0.0.0       | /8            |
-| A             | 9                  | 23              | 255.128.0.0     | /9            |
-| A             | 12                 | 20              | 255.240.0.0     | /12           |
-| A             | 14                 | 18              | 255.252.0.0     | /14           |
-| B             | 16                 | 16              | 255.255.0.0     | /16           |
-| B             | 17                 | 15              | 255.255.128.0   | /17           |
-| B             | 20                 | 12              | 255.255.240.0   | /20           |
-| B             | 22                 | 10              | 255.255.252.0   | /22           |
-| C             | 24                 | 8               | 255.255.255.0   | /24           |
-| C             | 25                 | 7               | 255.255.255.128 | /25           |
-| C             | 28                 | 4               | 255.255.255.240 | /28           |
-| C             | 30                 | 2               | 255.255.255.252 | /30           |
-
-```
 </b></details>
 
 <details>

The statement **[255] is assigned to a broadcast address** could be a bit misleading as this is not always the case in most networks. The subnet mask column in the example table also contradicts the former statement and could leave beginners totally confused. So instead of **255**, the **last address (on the host part)** of the network mask should have been used and this can be any number within the range of **0 and 255.**