if JL is KL+JK, then the equation you want to use is 5x+6+3x+6=28, then simplify into 8x+12=28, then subract 12 from both sides to get 8x=16, divide both sides by 8 and you get x=2, then you put 2 in for x in KL=5x+6 getting KL=5(2)+6 which simplified is KL=16