Answer
$\{ 1 \}$
Work Step by Step
Step 1. Graph $y=7x - 2x + 4 - 5$ as shown in the figure (red).
Step 2. Graph $y=3x + 1$ as shown in the figure (blue).
Step 3. Find the intersect at point $(1,4)$, thus $x=1$.
Step 4. The solution is $\{ 1 \}$