Let' begin by listing out the information given:
Number of marbles = 4; blue, blue, red, and green
Jenny pulls out two marbles without replacement. We have:
[tex]\begin{gathered} S=\mleft(Blue,Blue\mright),(Blue,Red),(Blue,Green) \\ S=(Red,Blue),(Red,Green) \\ S=(Green,Blue),(Green,Red) \\ \therefore S=\mleft\lbrace(BB),(BR),(BG),(RB),(RG),(GB),(GR)\mright\rbrace \end{gathered}[/tex]