5L=_ mL?
198g=_kg?
75mL=_L?

Hi there Sdsdancer! Okay, so, let me explain before i give the answer. Liters to Milliliters is always times 1000. For example, 3L=_ mL? would be 3L=3000 mL. So, the first would be 5L = 5000 mL. Next, is gram to kilogram. Now, fun fact: did you know there is a decimal at the end of EVERY number? No one shows it. We need this for Gram to kilogram, because we will move that decimal to the beginning of the number. for example, 256g=_kg? would be 256=0.256 kg. So, for this one, it would be 198g=0.198 kg. Now, the last on is trickier. For mL to L you need to move the number to the hundredths place. For example, 45mL=_L? would be 45mL=0.045L. So, this would be 75mL=0.075L. So, all the answers would be:         
5L=5000mL
198g=0.198kg
75mL=0.075L

I hope you understand, and most of all, I hope I helped!!! :D

Bwould be the answer