Answer:
Explanation:
Let's take for example the first one Al(C2H2O2)
If there is no subscript under the number, the amount of atoms is 1
If we have a subscript, as in this case, the subscript is the number of atoms.
In the example above, there is 1 atom of Aluminium, two of Carbon, two of Hydrogen and 2 of Oxygen. If you have parenthesis and number before them, e.g., 4(Al2O3), you just multiply the parenthesis by the number in front of them, which means 4*2=8 aluminium atoms, 3*4=12 oxygen atoms, the same applies if the number is subscript behind the parenthesis like in fourth example.