What is the chemical formula for nickel (III) oxide, I know the answer but can someone explain how you would get it?

the answer is d.

1. Write the symbols for each element.

2. Find the charge for each element using the Periodic Table. Write it above each element. (because there is a (III) after nickel, the charge of nickel is +3. oxygen is in group 16, which means it has a -2 charge.)

3. See if the charges are balanced (if they are you're done!)

- when you criss cross (getting Ni2O3, the charges are canceled out, so the equation is balanced.

if you still need help or if this is confusing, look up How to Write the Formula for Nickel (III) oxide  by Wayne Breslyn on YT.

the correct answer is a