Each chef at "Sushi Emperor" prepares
15
1515 regular rolls and
20
2020 vegetarian rolls daily. On Tuesday, each customer ate
2
22 regular rolls and
3
33 vegetarian rolls. By the end of the day,
4
44 regular rolls and
1
11 vegetarian roll remained uneaten.
How many chefs and how many customers were in "Sushi Emperor" on Tuesday?

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.