We start with the equation
\[
-\frac{1}{x-1} + \frac{2}{x-2} = \frac{3}{x^2 - 3x + 2}
\]
To find the least common denominator, we first factor the polynomial in the denominator on the right-hand side:
\[
x^2 - 3x + 2 = (x - 2)(x - 1)
\]
Next, we rewrite the left-hand side of the equation using the least common denominator \((x - 1)(x - 2)\):
\[
-\frac{1}{x-1} + \frac{2}{x-2} = -\frac{1 \cdot (x - 2)}{(x - 1)(x - 2)} + \frac{2 \cdot (x - 1)}{(x - 1)(x - 2)}
\]
This simplifies to:
\[
-\frac{x - 2}{(x - 1)(x - 2)} + \frac{2(x - 1)}{(x - 1)(x - 2)} = \frac{-x + 2 + 2x - 2}{(x - 1)(x - 2)} = \frac{x}{(x - 1)(x - 2)}
\]
Now we can set the left-hand side equal to the right-hand side:
\[
\frac{x}{(x - 1)(x - 2)} = \frac{3}{(x - 1)(x - 2)}
\]
Since the denominators are the same, we can equate the numerators:
\[
x = 3
\]
The solution to the equation is \( x = 3 \).