$\"\"$

Given the area of square with side x is 9. \ \

By known formula,

The area of square with side x is $\"\"$ . \ \ so,

$\"\"$

$\"\"$ (Square root on each side) \ \

$\"\"$ \ \ $\"\"$ (Square root: $\"\"$ ) $\"\"$

If $\"\"$ then $\"\"$ . \ \

The area of square with side 12 is $\"\"$ .

$\"\"$

$\"\"$ (Evaluate power: $\"\"$ ) $\"\"$

The option b is correct. \ \