Rival is a synonym of Equal. Equal is related to Math. Math is related to School. School is related to Trouble. 
Marine is a type of Soldier. Marine is related to Fish. Salmon is a type of Fish. 
Rival <--Synonym--> Equal <--RelatedTo--> Math <--RelatedTo--> School <--RelatedTo--> Trouble 
Soldier <--IsA-- Marine <--RelatedTo--> Fish <--IsA-- Salmon 