1. **State the problem:** Solve the system of equations using substitution: $$y = -8x + 10$$ $$2y - 4x = 40$$ 2. **Substitution method:** Since $y$ is already expressed in terms of $x$ in the first equation, substitute $y = -8x + 10$ into the second equation. 3. Substitute: $$2(-8x + 10) - 4x = 40$$ 4. Simplify the left side: $$-16x + 20 - 4x = 40$$ 5. Combine like terms: $$-20x + 20 = 40$$ 6. Subtract 20 from both sides: $$-20x = 20$$ 7. Divide both sides by $-20$: $$x = \frac{20}{-20} = -1$$ 8. Substitute $x = -1$ back into the first equation to find $y$: $$y = -8(-1) + 10 = 8 + 10 = 18$$ 9. **Final solution:** $$(x, y) = (-1, 18)$$