To find out how long it will take Stacy to paint the entire room, we first determine her rate of painting.
Stacy paints \( \frac{3}{4} \) of the room in 3 hours. To find out how long it takes to paint the entire room, we can set up a proportion.
If \( \frac{3}{4} \) of the room takes 3 hours, then 1 whole room would take \( x \) hours, which can be calculated as follows:
\[ \frac{3}{4} \text{ room} = 3 \text{ hours} \] \[ 1 \text{ room} = x \text{ hours} \]
Setting up the ratio:
\[ \frac{3}{4} : 3 = 1 : x \]
Cross multiplying gives us:
\[ 3x = 4 \cdot 3 \] \[ 3x = 12 \] \[ x = \frac{12}{3} = 4 \]
Thus, it takes Stacy 4 hours to paint the entire room. Therefore, the answer is:
4 hours