1. **State the problem:** A baker starts with $\frac{3}{4}$ cup of water. 2. He pours half of the water into the batter, so the amount poured is: $$\frac{1}{2} \times \frac{3}{4} = \frac{3}{8} \text{ cups}$$ 3. The remaining water in the cup after pouring is: $$\frac{3}{4} - \frac{3}{8} = \frac{6}{8} - \frac{3}{8} = \frac{3}{8} \text{ cups}$$ 4. Then he spills $\frac{1}{8}$ cup on the floor, so the water left in the cup is: $$\frac{3}{8} - \frac{1}{8} = \frac{2}{8} = \frac{1}{4} \text{ cups}$$ 5. The baker wants to have 50% more water than he started with. 50% more than $\frac{3}{4}$ cup is: $$\frac{3}{4} + 0.5 \times \frac{3}{4} = \frac{3}{4} + \frac{3}{8} = \frac{6}{8} + \frac{3}{8} = \frac{9}{8} = 1 \frac{1}{8} \text{ cups}$$ 6. To reach $\frac{9}{8}$ cups, the baker needs to add water to the $\frac{1}{4}$ cup left: $$\frac{9}{8} - \frac{1}{4} = \frac{9}{8} - \frac{2}{8} = \frac{7}{8} \text{ cups}$$ **Final answer:** The baker needs to add $\frac{7}{8}$ cup of water.