What is the symbol for an ion with 50 protons 48 electrons 68 neutrons?

Sn2+

Your protons equal the atomic number of an element: Sn (Tin).

The amount of protons and electrons will be the same if the atom is neutral. In this case, tin has lost two electrons and so tin is no longer neutral and becomes Sn2+

To double check, you would subtract the atomic number from the mass number of tin to see if the number of neutrons is equal to what has been provided.

mass number - atomic number = number of neutrons

118 - 50 = 68