R,RR,RR,R
R,{a}R,\{a\}R,{a}
R,{x∈R:x≥a}R,\{x \in R: x \geq a\}R,{x∈R:x≥a}
{x∈R:x>a},R\{x \in R: x>a\}, R{x∈R:x>a},R