1.)
Starts with 40:10, then cuz you have 80 buns, you need to x2, so it would be 20 cubes
2.)
I don’t know, sorry
3.)
4:2 and 60 in total
so 4+2 is 6 and 60/6 is 10
so it would be 40:20 so 20
hope this helps :)
The graph should look the the one I attached to this answer
This is something you would do through trial and error. At least, that's the approach I took. I'm not sure if there is any algorithm to solve. The solution I got is shown in the attached image below. There are probably other solutions possible. The trick is to keep each number separate but not too far away so that the other numbers to be filled in later don't get too crowded to their neighbor.
Side note: any mirror copy of what I posted would work as well since you can flip the page around and it's effectively the same solution.