Answer
The molecular formula is $C_{15}H_{32}$.
Work Step by Step
From the name of the compound, we first find out the number of carbons atoms.
Nonane = 9C atoms
Trimethyl = 3C atoms
Propyl = 3C atoms
Total 15 carbon atoms.
General formula of alkanes is $C_nH_{2n+2} $, where n is the number of carbons atoms.
In this case, n=15. So, the molecular formula is $C_{15}H_{32}$.