12 ist wie viel Prozent von 40?

$12$ $12$ is $30 %$ $color(green)(30%)$ of $40$ $40$

If $12$ $12$ is $x %$ $x%$ of $40$ $40$
dann
$XXX \frac{x}{100} \times 40 = 12$ $color(white)("XXX")x/100 xx 40 =12$

$XXX 40 x = 1200$ $color(white)("XXX")40x=1200$

$XXX x = 30$ $color(white)("XXX")x=30$