Answer :

Let's simplify each expression step-by-step and express the results with positive exponents.

### Part (i): [tex]\(\left(x^{-3}\right)^4\)[/tex]

To simplify this expression, we use the power of a power property of exponents, which states:
[tex]\[ (a^m)^n = a^{m \cdot n} \][/tex]

Here, [tex]\(a = x\)[/tex], [tex]\(m = -3\)[/tex], and [tex]\(n = 4\)[/tex]. So,

[tex]\[ \left(x^{-3}\right)^4 = x^{-3 \cdot 4} = x^{-12} \][/tex]

To express the result with a positive exponent, we use the property of exponents that states:
[tex]\[ a^{-m} = \frac{1}{a^m} \][/tex]

Therefore,

[tex]\[ x^{-12} = \frac{1}{x^{12}} \][/tex]

So, the simplified expression for (i) is:

[tex]\[ \left(x^{-3}\right)^4 = \frac{1}{x^{12}} \][/tex]

### Part (ii): [tex]\(3 x^{\frac{1}{6}} \times 3 x^{-\frac{7}{6}}\)[/tex]

First, we combine the coefficients:

[tex]\[ 3 \times 3 = 9 \][/tex]

Next, we combine the exponents of [tex]\(x\)[/tex] using the product of powers property, which states:
[tex]\[ a^m \times a^n = a^{m + n} \][/tex]

Here, we have [tex]\(x^{\frac{1}{6}}\)[/tex] and [tex]\(x^{-\frac{7}{6}}\)[/tex], so we add the exponents:

[tex]\[ \frac{1}{6} + \left(-\frac{7}{6}\right) = \frac{1}{6} - \frac{7}{6} = -\frac{6}{6} = -1 \][/tex]

Thus,

[tex]\[ x^{\frac{1}{6}} \times x^{-\frac{7}{6}} = x^{-1} \][/tex]

Now we have:

[tex]\[ 9 \cdot x^{-1} \][/tex]

To express this with a positive exponent, we use the property [tex]\(a^{-m} = \frac{1}{a^m}\)[/tex]:

[tex]\[ 9 \cdot x^{-1} = 9 \cdot \frac{1}{x} = \frac{9}{x} \][/tex]

Therefore, the simplified expression for (ii) is:

[tex]\[ 3 x^{\frac{1}{6}} \times 3 x^{-\frac{7}{6}} = \frac{9}{x} \][/tex]

### Final Simplified Results
So the final simplified results are:

(i) [tex]\(\left(x^{-3}\right)^4 = \frac{1}{x^{12}}\)[/tex]

(ii) [tex]\(3 x^{\frac{1}{6}} \times 3 x^{-\frac{7}{6}} = \frac{9}{x}\)[/tex]