To divide the polynomial \( x^3 - x^2 - 5x - 3 \) by \( x - 3 \), we can use polynomial long division.

**Step 1: Set up the division**
We are dividing \( x^3 - x^2 - 5x - 3 \) by \( x - 3 \).

**Step 2: Divide the leading term**
The first term in the dividend is \( x^3 \). Divide this by the leading term of the divisor \( x \):
\[
\frac{x^3}{x} = x^2
\]

**Step 3: Multiply and subtract**
Now, multiply \( x^2 \) by the whole divisor \( x - 3 \):
\[
x^2(x - 3) = x^3 - 3x^2
\]
Now, subtract this from the original polynomial:
\[
(x^3 - x^2 - 5x - 3) - (x^3 - 3x^2) = 2x^2 - 5x - 3
\]

**Step 4: Repeat the process**
Next, divide the leading term of the new polynomial \( 2x^2 \) by \( x \):
\[
\frac{2x^2}{x} = 2x
\]
Multiply \( 2x \) by \( x - 3 \):
\[
2x(x - 3) = 2x^2 - 6x
\]
Now, subtract this from \( 2x^2 - 5x - 3 \):
\[
(2x^2 - 5x - 3) - (2x^2 - 6x) = x - 3
\]

**Step 5: One more time**
Now divide \( x \) by \( x \):
\[
\frac{x}{x} = 1
\]
Multiply \( 1 \) by \( x - 3 \):
\[
1(x - 3) = x - 3
\]
Subtract:
\[
(x - 3) - (x - 3) = 0
\]

So, the division is complete, and the remainder is \( 0 \).

**Result:**
Thus,
\[
\frac{x^3 - x^2 - 5x - 3}{x - 3} = x^2 + 2x + 1
\]

Finally, we can express the division as:
\[
x^3 - x^2 - 5x - 3 = (x - 3)(x^2 + 2x + 1)
\]