1368.31 – What's That Fraction?

If $x$ is the fraction, then

$$\begin{aligned}\left( 2x + \dfrac{x}{2} \right) x &= x \\2x + \dfrac{x}{2} &= 1 \text{ (assuming } x \neq 0 \text{)} \\4 x + x &= 2\\5x &= 2 \\x &= \dfrac{2}{5}\end{aligned}$$

Two-fifths! That's the fraction. Run it through the problem's specs to make sure.