Can anyone help me with the answer for number 4

Answer:
b
Step-by-step explanation:
Given K is the midpoint of JL, then
JK = KL ← substitute values
6x = 3x + 3 ( subtract 3x from both sides )
3x = 3 ( divide both sides by 3 )
x = 1
Hence
JK = 6x = 6 × 1 = 6
KL = 3x + 3 = (3 × 1) + 3 = 3 + 3 = 6
JL = 6 + 6 = 12