$\"\"$

45 is compared the 15. So, 45 is the part and 15 is the whole.

$\"\"$ (Percent proportion)

$\"\"$

Apply cross multiplication property: $\"\"$ , when $\"\"$ .

$\"\"$

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

$\"\"$ (Divide each side by 15)

$\"\"$ (Cancel common terms)

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

The 45 is $\"\"$ of 15.