1. **State the problem:** Solve for $x$ in the equation $3 \cdot (-2.5) = x$. 2. **Formula and rules:** Multiplication of a positive number by a negative number results in a negative number. 3. **Calculate:** $$x = 3 \times (-2.5)$$ 4. **Intermediate step:** $$x = \cancel{3} \times (-2.5)$$ 5. **Simplify:** $$x = -7.5$$ 6. **Answer:** The value of $x$ is $-7.5$.