Answer:
9
Explanation:
In a chemical equation, the subscript numbers next to each element's symbol tell us how many atoms of that element are in the substance. So, for example, in H₂O, there are 2 atoms of hydrogen since there is a "₂" next to the H.
What's next to our H in C₄H₉? It looks like "₉," so we can determine that there are 9 hydrogen atoms in C₄H₉ (which is butyl, by the way).
Hopefully that's helpful! :)
