Shelves with 3 cars: 10
Shelves with 2 cars: 6
Total:42
Shelves with 3 cars: 6
Shelves with 2 cars: 12
Total:42
There are many ways to do this. So what I did was multiply 3 by a number like 10. Then I took the 2 and multiplied it by 3. i added the numbers 30+6=36. that doesn't work so i tried 2 multiplied by 6. 30+12=42. Hope this helped a little. :D