How many hydrogen atoms are there in 5 molecules of c3h7o

There would be 45 hydrogen atoms.

Explanation:

The only thing you need to focus on is hydrogen, since thats what the questions wants. With that said, take away every other part of the molecule.

ONLY KEEP WHATS ATTACHED TO THE H.

It says that there are 7 Hydrogen atoms in the molecule right? So you take the 7 and multiply it by the 5 molecules that they want. (7x5=45)

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.