Resposta:
[tex]\textsf{Leia abaixo}[/tex]
Explicação passo a passo:
[tex]\mathsf{(a + 3)x = 15}[/tex]
[tex]\mathsf{(-3 + 3)x = 15 \iff indetermina}\varsigma\textsf{\~a}o}[/tex]
[tex]\mathsf{(-2 + 3)x = 15 \iff x = 15}[/tex]
[tex]\mathsf{(-1 + 3)x = 15 \iff 2x = 15 \iff x = \dfrac{15}{2}}[/tex]
[tex]\mathsf{(0 + 3)x = 15 \iff 3x = 15 \iff x = 5}[/tex]
[tex]\mathsf{(1 + 3)x = 15 \iff 4x = 15 \iff x = \dfrac{15}{4}}[/tex]
[tex]\mathsf{p(A) = \dfrac{casos\:favor{\'a}veis}{casos\:poss{\'i}veis}}[/tex]
[tex]\boxed{\boxed{\mathsf{p(A) = \dfrac{2}{5} = 40\%}}}[/tex]