Systems of Two Linear Equations in Two Variables

Multiply first by 10: $5x + 2y = 50$. With $x = y + 4$: $5(y+4) + 2y = 50$ → $7y = 30$ → $y \approx 4.3$. Recompute with $y - x = 4$ → $x = y - 4$: $5(y-4) + 2y = 50$ → $7y = 70$ → $y = 10$.