Question

Num total de R$ 300,00, a quantia de R$ 21,00 equivale a quanto porcento?

Answer 1

300       100%
21          x
-           -


300x=21 x 100
x=2100/300
x=7%

Answer 2

300 corresponde a 100%
21 corresponde a x%
Assim:

$x= \frac{21*100}{300} \\ \\ x=\frac{21}{3} =7$

Logo:

$x=7%$

21 Equivale a 7%.