Make a table of values for x + y = 6 and another for x - y = 2, using whole numbers x = 0 to 6…

Step 1. First table. The points are $(0, 6)$, $(1, 5)$, $(2, 4)$, $(3, 3)$, $(4, 2)$, $(5, 1)$ and $(6, 0)$.

Step 2. Second table. The points are $(2, 0)$, $(3, 1)$, $(4, 2)$, $(5, 3)$ and $(6, 4)$.

Step 3. The common point. Only $(4, 2)$ is in both tables, and the two lines cross there.

Step 4. Check. $4 + 2 = 6$ and $4 - 2 = 2$.