Hi there!
We know that JK and KL are congruent, meaning they equal the same thing.
So, if KL is 3, we could also say that JK is 3 as well, because they are congruent.
If you add JK and KL together, you would get 6.
Now, because they are also adjacent, your equation would look like this...
JK + KL = JL
Now, plug in what you know...
3 + 3 = 6.
In summary, your answer would be
JL = 6.
I hope that helped!
(I find drawing diagrams helps me a lot with these types of problems. Maybe it will do the same for you!)
:)