Explanation:
First of all , there were a total charge of +13e (6 protons from carbon and 7 protons from nitrogen), that meant there requires to be a total charge of +13e after the collision occurred. Listed is 16 protons (+16e), 3 antiprotons (-3e), 8 positrons (+8e) and 16 neutral particles (0e), so the total charge listed is +21e, meaning an excess of +8e, meaning you need 8 electrons (-8e) to balance out the charge.
