Question

Qual deve ser o capital qualificado a uma taxa de juros simples de 25% ao ano para que em 6 meses renda R$ 425,00 de juro?

Answer 1

J=C*I*T
425=C*25*0,5
           100
42500=12,5C
C=42500
      12,5
C=3400

Answer 2

$\sf\large \boxed{\boxed{\tt J = C \cdot i \cdot t}}$

_______________________

$\sf \displaystyle 425\:=\:C\:\cdot 0,\:25\:\cdot \left(\frac{1}{2}\right)\\\\\\\sf \boxed{\star \sf \ {Troque \:os \:lados} }\\\\\\\sf C\cdot \:0.25\left(\frac{1}{2}\right)=425\\\\\\\sf C\frac{0.25}{2}=425\\\\\\\sf 2C\frac{0.25}{2}=425\cdot \:2\\\\\\\sf 0.25C=850\\\\\\\sf \frac{0.25C}{0.25}=\frac{850}{0.25}\\\\\\\\\large \to \boxeed{\boxed{\sf C=3400}}$