What is the missing value of y?

X 5 10 15 20

y 3 6? 12

since x is a multiple of 5

similarly y is multiple of 3

so 3 6 9 12

9 is the missing value of y.

Step-by-step explanation:

So what you want to do here is simple, spot the pattern

6-3=3

3-0=3

13-6=6, so therefore, the missing value must be half of this, since it is only skipping one value in the pattern, making the answer 3.