Solution: Let the number of mackerel be $ m $. The ratio $ 5:4 = 20:m $ implies $ \frac{5}{4} = \frac{20}{m} $. Cross-multiplying: $ 5m = 80 $ → $ m = 16 $. There are $ \boxed{16} $ mackerel.

Mon, 04 May 2026 19:40:51 +0000

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