Substitution Method 415Aaa

1. **State the problem:** Solve the system of equations using substitution: $$x + 4y = 9$$ $$x + 5y = 13$$ 2. **Isolate one variable:** From the first equation, isolate $x$: $$x = 9 - 4y$$ 3. **Substitute into the second equation:** Replace $x$ in the second equation with $9 - 4y$: $$9 - 4y + 5y = 13$$ 4. **Simplify and solve for $y$:** $$9 + y = 13$$ $$y = 13 - 9$$ $$y = 4$$ 5. **Substitute $y$ back to find $x$:** Use $x = 9 - 4y$: $$x = 9 - 4 \times 4$$ $$x = 9 - 16$$ $$x = -7$$ 6. **Final solution:** $$x = -7, \quad y = 4$$