Respuesta :
30+50+20=100 = altogether marbles
P(white)= 20/100 =1/5
P(white)=1/5
P(white)= 20/100 =1/5
P(white)=1/5
[tex]|\Omega|=100\\
|A|=20\\
P(A)=\dfrac{20}{100}=\dfrac{1}{5}=20\%[/tex]