3 ethyl, 4 methylheptane. The compound is named by first identifying the longest carbon chain in the structure. in this case the chain has seven carbon atoms thus the prefix hept-.
Next you identify the substituent groups attached to the long carbon chain and name them from the lowest value of the integer assigned to the carbon atoms from either side. From the right, the ethyl group is attached to carbon number 3 while from the left, the methyl group is attached to carbon number 4. We therefore start with the right and name the attached groups first, including the carbon atoms to which they are attached.
Then we also take into consideration the highest number of bonds between the carbon atoms which is one from the question. Thus the suffix -ane is added if a maximum of one bond, -ene,if two bonds and -yne if three bonds.
