How many total atoms of each indicated element are present in CH3(CH2)14CH3?

In each -CH₃ group, there are 1 C atom and 3 H atoms.
In each -CH₂- group, there are 1 C atom and 2 H atoms.
(-CH₂-)₁₄ means there are 14 -CH₂- groups.

In a molecule of CH₃(CH₂)₁₄CH₃ :
Number of C atoms = 1 + 1×14 + 1 = 16
Number of H atoms = 3 + 2×14 + 3 = 34

It is a simple chain of 16 carbons, with 34 hydrogen atoms, all linked together with simple bonds.
Hexadecane

Hexadec- means "six and ten" (for the sixteen -- it is from the Latin)

-ane (in this context) means that the chain of carbon uses only single valence bonds.

To calculate it from the formula you gave us:
C
the first C (the one that has 3 hydrogen atoms tied to it) = 1 C and 3 H
then the middle part of the chain is made up of 14 sets having one carbon and 2 hydrogen each = 14 C and 28 H
The last C has 3 hydrogens = 1 C and 3 H

Add them up.

16 atoms C
34 atoms H