Resposta :
Segundo o enunciado:
[tex]\text{A}=\{\text{a}, \text{b}, \text{c}\}[/tex]
Considere o elemento [tex]\text{d}[/tex].
Desta maneira, [tex]\text{B}=\{\text{a}, \text{b}, \text{c}, \text{d}\}[/tex]
Observe que, [tex]\text{P}(\text{A})=3[/tex] e [tex]\text{P}(\text{B})=4[/tex].
Logo, [tex]\dfrac{\text{P}(\text{B})}{\text{P}(\text{A})}=\dfrac{4}{3}[/tex]