Answer :

Let's simplify the expression [tex]\(\frac{1}{7 \sqrt{3} + 5 \sqrt{6}}\)[/tex].

### Step 1: Multiply by the Conjugate

To rationalize the denominator, we multiply the numerator and the denominator by the conjugate of the denominator. The conjugate of [tex]\(7 \sqrt{3} + 5 \sqrt{6}\)[/tex] is [tex]\(7 \sqrt{3} - 5 \sqrt{6}\)[/tex].

So, we have:

[tex]\[ \frac{1}{7 \sqrt{3} + 5 \sqrt{6}} \times \frac{7 \sqrt{3} - 5 \sqrt{6}}{7 \sqrt{3} - 5 \sqrt{6}} = \frac{7 \sqrt{3} - 5 \sqrt{6}}{(7 \sqrt{3} + 5 \sqrt{6})(7 \sqrt{3} - 5 \sqrt{6})} \][/tex]

### Step 2: Simplify the Numerator

The numerator simplifies directly to:

[tex]\[ 7 \sqrt{3} - 5 \sqrt{6} \][/tex]

### Step 3: Simplify the Denominator

Now, we need to simplify the denominator. Recall the difference of squares formula [tex]\((a + b)(a - b) = a^2 - b^2\)[/tex]. Applying it here:

[tex]\[ (7 \sqrt{3} + 5 \sqrt{6})(7 \sqrt{3} - 5 \sqrt{6}) = (7 \sqrt{3})^2 - (5 \sqrt{6})^2 \][/tex]

Calculating each term:

[tex]\[ (7 \sqrt{3})^2 = 49 \cdot 3 = 147 \][/tex]

[tex]\[ (5 \sqrt{6})^2 = 25 \cdot 6 = 150 \][/tex]

So, the denominator becomes:

[tex]\[ 147 - 150 = -3 \][/tex]

### Step 4: Put It All Together

Now, we can put together our numerator and denominator:

[tex]\[ \frac{7 \sqrt{3} - 5 \sqrt{6}}{-3} \][/tex]

### Step 5: Simplify

Separate the numerator over the denominator:

[tex]\[ \frac{7 \sqrt{3}}{-3} - \frac{5 \sqrt{6}}{-3} = -\frac{7 \sqrt{3}}{3} + \frac{5 \sqrt{6}}{3} \][/tex]

So, the simplified form of [tex]\(\frac{1}{7 \sqrt{3} + 5 \sqrt{6}}\)[/tex] is:

[tex]\[ -\frac{7 \sqrt{3}}{3} + \frac{5 \sqrt{6}}{3} \][/tex]

This is your final answer:

[tex]\[ \boxed{-\frac{7 \sqrt{3}}{3} + \frac{5 \sqrt{6}}{3}} \][/tex]