To find out how long Jeff practiced during the week, we need to multiply the number of practices by the duration of each practice.
Jeff has practice 3 times, and each practice lasts \( \frac{3}{4} \) hour.
Calculating the total time:
\[ 3 \text{ practices} \times \frac{3}{4} \text{ hour/practice} = \frac{3 \times 3}{4} = \frac{9}{4} \text{ hours} \]
Now, we need to convert \( \frac{9}{4} \) hours into a mixed number:
\[ \frac{9}{4} = 2 \frac{1}{4} \text{ hours} \]
Thus, the total practice time is \( 2 \frac{1}{4} \) hours.
The correct answer is B. 2 1/4 hours.