R + S means 'R is the daughter of S'

R = S means 'R is the father of S'

R ÷ S means 'R is the wife of S'

R × S means 'R is the brother of S'

E ÷ F × J + L = M, then how is L related to E?

Father-in-law

ATQ, 

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Please note:

  l   ⇒ Vertical line shown "generation gap".

 =  ⇒ Double lines shown "relation of spouse" 

—  ⇒ Horizontal line shown "relation in same generation other than spouse".

     ⇒ Rectangular box shown " Male".

     ⇒ Circular box shown " Female".

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