The answer is ; 68
Explain
JM= ML substitute values to get
3x+4=5x-16
add 16
subtract 3x from both side to
get 20 =2x
divide by 2
get x= 10
So
50 JM =3x 10+4=34
so JL = 2JM
substitute value to get
JL=2 x34
That should equal to 68
Do you have any doubts?