Resposta :
Juros simples:
[tex]\boxed{J=Cit}[/tex]
[tex]C=\text{R\$12.000,00}\\\\ t=5\ \text{meses}=\dfrac{5}{12}\ \text{ano}\\\\ i=10\%\ \text{a.a.}=0.1\ \text{a.a.}[/tex]
[tex]J=12000(0.1)\bigg(\dfrac{5}{12}\bigg)=100(5)\ \therefore\ \boxed{J=\text{R\$500,00}}[/tex]