Step-by-step explanation:
When we place a number before the chemical formula of a compound then it represents the number of molecules of that compound.
For example, in
the number 3 represents that there are 3 molecules of ammonia.
Whereas a subscript in a chemical formula tells us the number of atoms of an element present in the compound.
For example, in
the number 4 is a subscript and it represents that there are 4 atoms of hydrogen are present.
Thus, we can conclude that the numbers 3 and 4 refer to the number of molecules and number of hydrogen atoms in
.