What is 2.7 kl = ? cause its kinda hard and i'm in 5th grade and don't call me stupid but i just don't know it

Please ! ! !  Nobody is ever going to call you stupid for asking a question !
If that ever happens, you let me know, and I'll have a little talk with that person.

  2.7 K L

I can't be completely sure exactly what that means.  In math and science,
there are no rules about what letter you MUST use to represent something. 
There are a lot of habits, but no rules.  So I can't be sure of what ' K ' stands
for or what ' L ' stands for.  The best I can do is take some guesses and show
you how it works:

' K '
A lot of times in math and science ' K ' means ' 1,000 '.  (one thousand).
Instead of writing  1,000  people will often write K .
So ' 2.7 K L ' could mean ' 2.7 thousand of L '.
That would be the same thing as ' 2,700 L '.

' L '
This could mean anything.  That's why, when you start writing your own
equations, or your own problems for other people to solve, and you use
letters in them, it's really important to explain what the letters mean.

One possibility ... ' L ' could stand for 'Liter'.  The Liter is a metric unit of volume measurement.  It's a tiny bit more than a quart of milk. 

There's no way to know for sure, unless someone tells us. But if that's what this
' L ' stands for, then  ' 2.7 K L ' could mean ' 2,700 Liters ' of water, milk, gas, or
empty space.

It’s -1 is the answer for your question