The correct answer is: -3 (minus three)
Step-by-step explanation:
To find the overall charge, we add electrons and protons. Make sure that you use the negative sign for an electron and positive sign for proton.
There are 10 electrons. It means the charge is "-10"
There are 7 protons. It means the charge is "+7"
Add both of them:
+7 - 10 = -3
Therefore the overall charge on this ion is -3.