Answer :
Fatty acid => hydrocarbon chain + carboxilic group => CnHm-COOH
8 carbons long => C - C - C - C - C - C - C - C - COOH
unsaturated => double bonds
=> CH3-CH=CH-CH2-CH2-CH2-CH2-CH2 - COOH: 8 carbon chain, one double bond, carboxylic group.
8 carbons long => C - C - C - C - C - C - C - C - COOH
unsaturated => double bonds
=> CH3-CH=CH-CH2-CH2-CH2-CH2-CH2 - COOH: 8 carbon chain, one double bond, carboxylic group.