I don't see the relation

Algebra Level 2

$\begin{aligned} \large \color{#3D99F6}2^{\color{#624F41}x} - \color{#3D99F6}2^{\color{#624F41}y} & = & \large 1 \\ \\ \large \color{#20A900}4^{\color{#624F41}x}- \color{#20A900}4^{\color{#624F41}y} & = & \large { \frac 5 3} \\ \\ \\ \large {\color{#624F41}x} - {\color{#624F41}y} & = & \large \, ? \end{aligned}$

Details and Assumptions:

$x$ and $y$ are real numbers.