Write coordinates of 2 points which lie on line x + y = 8. How many such points exist?

By inspection, x = 0 and y = 8 is a point on x + y = 8 because 0 + 8 = 8, it satisfies.

Let x = 1, then y = 7. So, the point (1,7) also satisfies.

So, coordinates of two points are (0, 8) and (1,7).

Since, we can take infinitely such real values of x and y which satisfy given equation. So, infinitely many points exist.