1. **State the problem:** B has completed $3 \frac{3}{4}$ km of a 5 km race. We need to find how many kilometers she has left to complete. 2. **Convert mixed fraction to improper fraction:** $3 \frac{3}{4} = \frac{3 \times 4 + 3}{4} = \frac{12 + 3}{4} = \frac{15}{4} = 3.75$ km 3. **Use the formula:** Distance left = Total distance - Distance completed 4. **Calculate the distance left:** $5 - 3.75 = 1.25$ km 5. **Interpretation:** B has $1.25$ km left to complete the race.