please solve this it is my first worksheet of third quarter and i cant start off with a d or f i will get killed

Answer:
40
Step-by-step explanation:
It's basically reverse-simplifying. You can cross multiply, but for me, the easiest thing is to look and see how 3 turned in to 12. To get 12 from 3, you multiply by 4. So then multiply 10 by 4 and you get 40. Hope this helps!! :)