1L = 33.814 oz
xL = 2.75 oz
so it's a proportion
1L / 33.814 oz = xL / 2.75
solve for x
(1/33.814) * 2.75 = 0.0813272609 on your calculator, but it's not the answer.
the number in your problem, 2.75 oz, has 3 significant figures. so you can only round this number to 3 significant figures too.
your equipment isn't accurate enough to give a reading to 10 significant figures if that makes sense. you have to give the answer in terms of the term you use with the lowest significant figures.
so with 3 significant figures,
0.0813272609 rounds to
0.0813 L