The total number of boron - oxygen bonds in borax is 'x' and boron - oxygen - boron bonds are 'y'. Then the value of `x-y` is :

Answer

To solve the problem regarding the number of boron-oxygen bonds (denoted as \( x \)) and boron-oxygen-boron bonds (denoted as \( y \)) in borax, we will follow these steps:

### Step 1: Identify the chemical formula of borax
The chemical formula of borax is sodium tetraborate decahydrate, which can be represented as \( \text{Na}_2\text{B}_4\text{O}_7 \cdot 10\text{H}_2\text{O} \).

### Step 2: Draw the structure of borax
To understand the bonding, we need to visualize the structure of borax. Borax consists of four boron atoms and seven oxygen atoms. The arrangement can be visualized as follows:

- Each boron atom is connected to oxygen atoms.
- Some oxygen atoms are shared between boron atoms, forming boron-oxygen-boron (B-O-B) bonds.

### Step 3: Count the total number of boron-oxygen bonds (\( x \))
In the structure, we can count the boron-oxygen bonds. Each boron atom typically forms bonds with oxygen atoms. By analyzing the structure, we find:

1. Each of the four boron atoms forms bonds with oxygen.
2. Counting these connections, we find that there are a total of **12 boron-oxygen bonds**.

Thus, \( x = 12 \).

### Step 4: Count the number of boron-oxygen-boron bonds (\( y \))
Next, we need to count the boron-oxygen-boron bonds. These bonds occur where an oxygen atom connects two boron atoms. By examining the structure, we can identify:

1. There are five distinct boron-oxygen-boron connections in the structure.

Thus, \( y = 5 \).

### Step 5: Calculate \( x - y \)
Now that we have both values:
- \( x = 12 \)
- \( y = 5 \)

We can calculate \( x - y \):
\[ x - y = 12 - 5 = 7 \]

### Final Answer
The value of \( x - y \) is **7**.

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