Respuesta :

twvogels
[tex]Probability=\frac{desired}{total}[/tex]
[tex]0.3=\frac{21}{N}[/tex]
[tex]0.3N=21[/tex]
[tex]N=\frac{21}{0.3}[/tex]
[tex]N=70[/tex]

There are 70 total marbles.