Question

A set X consists of all real numbers greater than or equal to 1. Use set-builder notation to define X.

Answer 1

We know that
The standard form of set-builder notation is  
{ x | “x satisfies a condition” } 
This set-builder notation can be read as “the set of all x such that x (satisfies the condition)”.

In this problem, there are 2 conditions that must be satisfied:

1st: x must be a real number
In the notation, this is written as “x ε R”.
Where ε means that x is “a member of” and R means “Real number”

 2nd: x is greater than or equal to 1
This is written as “x ≥ 1”

 therefore

Combining the 2 conditions into the set-builder notation:
X = { x | x ε R and x ≥ 1 } 

the answer is
X = { x | x ε R and x ≥ 1 }