1. **State the problem:** Solve the equation $$(x - 2500) \times 40\% - 21x = 900$$ for $x$. 2. **Rewrite the percentage as a decimal:** $40\% = 0.40$. 3. **Substitute and expand:** $$0.40(x - 2500) - 21x = 900$$ $$0.40x - 0.40 \times 2500 - 21x = 900$$ $$0.40x - 1000 - 21x = 900$$ 4. **Combine like terms:** $$0.40x - 21x = 900 + 1000$$ $$-20.6x = 1900$$ 5. **Solve for $x$:** $$x = \frac{1900}{-20.6}$$ $$x \approx -92.23$$ **Final answer:** $$x \approx -92.23$$