Answer: The correct option is D, i.e.,30.
Step-by-step explanation:
It the given equation we have two units l and dl.
Where l represents the liter and dl represents the deciliter. These are the volume units.
We know that,
1 liter = 10 deciliter
It means,
1 l = 10 dl
Multiply both sides by 3,
1\times 3 l = 10\times 3 dl
3 l = 30 dl
Therefore, the correct option is D and 3 l = 30 dl.