1. **State the problem:** We have a function machine where the input is $-2$, it is first multiplied by an unknown value $x$ (the question mark), then multiplied by $-3$, and the output is $-18$. 2. **Write the equation:** The process can be written as: $$-2 \times x \times -3 = -18$$ 3. **Simplify the left side:** Multiply the known numbers: $$(-2) \times (-3) = 6$$ So the equation becomes: $$6 \times x = -18$$ 4. **Solve for $x$:** Divide both sides by 6: $$x = \frac{-18}{6}$$ 5. **Show cancellation:** $$x = \frac{\cancel{-18}}{\cancel{6}} = -3$$ 6. **Answer:** The value that replaces the question mark is $-3$. This means the unknown multiplier in the function machine is $-3$ to produce the output $-18$ when the input is $-2$.