CH2-CH3 CH3-CH2-CH2-CH-CH-CH2-CH3 CH3

The structure corresponds to a seven-carbon main chain (heptane) with:

• an ethyl substituent on carbon 4
• a methyl substituent on carbon 3 (when numbered from the right end to give the lowest locants)

Therefore, the IUPAC name is: 4-ethyl-3-methylheptane

(Alphabetical order places ethyl before methyl: 4-ethyl-3-methylheptane.)