The question requires us to identify the number of electrons in an ion with charge -2 and atomic number 22.
The atomic number of an atom refers to the number of protons that this atom contains: in the case given by the question, the atom presents atomic number = 22, thus it contains 22 protons.
In a neutral atom, the number of protons (positively charged particles) and electrons (negatively charged particles) is the same. Thus, if the atom considered by the question was neutral, it would present 22 electrons.
Since we are considering an ion, the balance between the number of protons and electrons doesn't exist anymore. In this case, it is an anion, which means it presents more electrons than protons.
The charge -2 of the ion means it has two additional negative particles (electrons) compared to the number of positive particles (protons): thus, the ion given by the question presents 22 + 2 electrons = 24 electrons.