Question

12 reais corresponde a 15% de quanto?

Answer 1

x=12*100/15
x=1200/15
x=80
Resposta: R$80,00

Answer 2

12 ---- 15%
 x  ---- 100%

$\frac{12}{x} = \frac{15}{100} \\ x \times 15 = 12 \times 100 \\ 15x = 1200 \\ x = 1200 \div 15 \\ x = 80$

12 reais corresponde a 15% de 80 reais.