$\"\"$

The word $\"\"$ t is to 21 $\"\"$ represents the expression $\"\"$ .

The word $\"\"$ as $\"\"$ means equal and its symbol $\"\"$ .

The word $\"\"$ 40 is to 28 $\"\"$ represents the expression $\"\"$ .

The word $\"\"$ t is to 21 as 40 is to 28 $\"\"$ represents the proportion $\"\"$ . $\"\"$

The proportion is $\"\"$ .

Multiply each side by 21.

$\"\"$

Cancel common terms.

$\"\"$

$\"\"$ . $\"\"$

The value of $\"\"$ .