Answer is JK = 48.56
Step by step
We can add both line segments JK and KL together to equal JL (138)
4x + 6 + 7x + 15 = 138
Combine like terms
11x + 21 = 138
Subtract 21 from both sides to isolate variables
11x + 21 - 21 = 138 - 21
11x = 117
Divide both sides by 11 to solve
X = 10.64
Now we are looking for JK which is stated to be 4x + 6
Substitute our x value in for x
4 (10.64) + 6
42.56 + 6
JK = 48.56