How many carbon atoms C3H8 has 3.92 X 10^24 H atoms

There would be 1.47 x 10^24 carbon atoms in the sample.

Explanation:

If I've understoof the question, you mean you have a sample of C3H8 that contains 3.92 x 10^24 H atoms and want to know how many carbon atoms there are in that sample.

You can figure that out using the ratio of C atoms to H atoms, 3:8.

3.92 x 10^24 H atoms x 3 C atoms/8 H atoms = 1.47 x 10^24 C atoms