Please help me get the right answer I’ll give you points please please

STEP 1:
find number of liters in 30 deciliters

1 deciliter= 0.1 liter

multiply total number of deciliters (30) by liters in one deciliter (0.1).

=30 * 0.1 liter
=3 liters

STEP 2:
subtract 1 liter from step 1 answer because he already has one liter

= 3 liters - 1 liter
= 2 liters still needed

ANSWER: He needs to buy 2 liters

Hope this helps! :)