To solve for $x$, we are given two equations:

$y = 4x \quad \text{(Equation 1)}$ $y = 40 \quad \text{(Equation 2)}$

Since both equations express $y$, we can set them equal to each other:

$4x = 40$

Now, solve for $x$ by dividing both sides of the equation by 4:

$x = \frac{40}{4} = 10$

Thus, the solution is:

$x = 10$

Would you like more details on how this was solved or have any questions?

Here are five related questions you might explore:

1. What if the equation was $y = 3x$ and $y = 27$? What would $x$ be?
2. How would you solve $y = 5x + 3$ when $y = 28$?
3. Can you solve for $x$ if $y = 4x^2$ and $y = 64$?
4. How does solving for $x$ change if $y = 4x - 8$ and $y = 32$?
5. What happens if you add another equation like $y = 2x + 5$? How would you solve it?

Tip: When you solve equations, always make sure you properly isolate the variable by performing the same operations on both sides of the equation.