I am going to assume these are points across the same line. (line segments)
If so, then jk + kl = jl
If jk is 6x and kl is 3x, we can solve for x.
6x + 3x = 27 (note we subbed 27 in for jl)
9x = 27 (divide both sides by 9 to leave on x on the left)
x = 3
CHECK! sub 3 in for x in the original problem.
6 (3) + 3 (3) = 27
18 + 9 = 27
Yes! It checks. x = 3