1. **State the problem:** Solve the system of simultaneous equations: $$3x + y = 20$$ $$y = 2x$$ 2. **Use substitution method:** Since $y$ is already expressed in terms of $x$ in the second equation, substitute $y = 2x$ into the first equation. 3. **Substitute and simplify:** $$3x + 2x = 20$$ $$5x = 20$$ 4. **Solve for $x$:** $$x = \frac{20}{5} = 4$$ 5. **Find $y$ using $y = 2x$:** $$y = 2 \times 4 = 8$$ 6. **Final answer:** The solution to the system is $$x = 4, \quad y = 8$$ This means the two lines intersect at the point $(4, 8)$.