Answer
$x = 8$
Work Step by Step
To solve a proportion, we use the cross products property, multiplying the numerator of one ratio with the denominator of the other ratio, and vice versa:
$12(14) = 21x$
Multiply on the left side of the equation:
$168 = 21x$
Divide each side of the equation by $21$ to solve for $x$:
$x = 8$