Answer:
9
Step-by-step explanation:
Use rule of three
15 => 20
x => 12

x = 9
Answer:
307.5
Step-by-step explanation:
Well, y=1/3x
If you divide 3x/1 you'll get 3x/1
so that means y=1
then the equation is still y=1/3x because we divide 3/1
so yes it is proportional. :D