By the transversal theorem, if segments on a transversal cut by parallel lines are equal, then similar segments cut by the same parallel lines on another transversal are also equal.
Therefore
JK=KL=LM=5
=>
JM=3*5=15
23 is the middle number from 12 to 34.
The table is incorrect.
The correct table would be:
0-5
1-4.8
2-4.6
3-4.4
4-4.2
5-4.0
6-3.8
650 -136=514
514 divided by 25 = 20.56
So it would be 21
This will give you a little extra chairs but they have to be equal in each row