Answer: [tex]\bold{\dfrac{1}{35}}[/tex]
Step-by-step explanation:
[tex]\text{1st draw}\ and\ \text{2nd draw}\\\\\dfrac{4\ blue}{21\ total}\times \dfrac{3\ remaining\ blue}{20\ total\ remaining}=\dfrac{4\times3}{21\times20} = \dfrac{1}{7\times5}=\dfrac{1}{35}[/tex]