The diagram shows part of a straight line graph obtained by plotting $\frac{1}{y}$ against $\frac{1}{x}$. Express $y$ in terms of $x$.

1. Calculate the gradient of the straight line.

Let $Y = \frac{1}{y}$ and $X = \frac{1}{x}$.
Gradient $m = \frac{4 - 3}{4 - 2} = \frac{1}{2}$

2. Find the equation of the straight line in terms of $X$ and $Y$.

$Y - 3 = \frac{1}{2}(X - 2)$
$Y = \frac{1}{2}X - 1 + 3$
$Y = \frac{1}{2}X + 2$

3. Substitute the original variables back into the equation.

$\frac{1}{y} = \frac{1}{2}\left(\frac{1}{x}\right) + 2$
$\frac{1}{y} = \frac{1}{2x} + 2$

4. Rearrange to express $y$ in terms of $x$.

$\frac{1}{y} = \frac{1 + 4x}{2x}$
$y = \frac{2x}{1 + 4x}$