What is xer in math?

x ∈ R just means that x is a real number (can be any number, fraction, decimal, whole, positive, negative) x ∈ Z means that x is an integar (a positive or negatie whole number e.g. -2,0, 9, -32 etc) At the end of a question it is really just there to give you a way to check if your answer is correct, if it said x ∈ Z ...