Answer:
3 recipes/week
Explanation:
Pick any two points where the line passes to a point in the grid, so you don't go crazy with counts. That means (0.0) (1;3) (2;6) (3;9) Pick two of them, in order. Let's say we like (0.0) and (1.3) since we're lazy. Now let's subtract the second part of each pair, (in our case, 0-3), do it for the first pair (in our case 0-1) and divide the two results:
Feel free to pick any other two and double check, being careful you're always doing