To find out what number 36 is 80% of, you can set up the equation:
\[ 36 = 0.8 \times x \]
where \( x \) is the unknown number you are trying to find.
To solve for \( x \), you can divide 36 by 0.8:
\[ x = \frac{36}{0.8} \]
Calculating that gives:
\[ x = 45 \]
So, 36 is 80% of 45.