"The cooks in the kitchen cook with gas."
Translation:De koks in de keuken koken op gas.
It is "on" and not "with" because you cook on a stove that is powered by gas. But it would seem that "cooking on gas" is acceptable English too (British vs. American - http://idioms.thefreedictionary.com/be+cooking+on+gas). If that answer isn't accepted, maybe we should suggest it.