$\"\"$ $\"\"$

The expression is “twelve is one fifth of a number”.

Let $\"\"$ represent the number.

The word “is” can be represented as “ $\"\"$ ” symbol. $\"\"$

Rewrite the sentence into expression as

$\"\"$

The equation is $\"\"$ $\"\"$

According to multiplication property of equality: Multiply each side by 5.

$\"\"$

$\"\"$ (Cancel common terms)

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

The number is $\"\"$ .