$\"\"$

The percent is 30 $\"\"$ , and the part is 21.

Let n represent the whole.

The percent proportion is $\"\"$ .

Apply cross product property of equality: $\"\"$ then $\"\"$ .

$\"\"$

$\"\"$ (Multiply: $\"\"$ ) $\"\"$

Apply division property of equality: Divide each side by 30.

$\"\"$

$\"\"$ (Cancel common terms)

$\"\"$ (Divide: $\"\"$ ) $\"\"$

21 is 30 $\"\"$ of 70.