1. **Stating the problem:** We need to find the amount of sugar mixture used in the cake after setting aside 1/4 cup for the crumb topping. 2. **Given quantities:** - Brown sugar: $\frac{3}{8}$ cup - White sugar: $\frac{1}{3}$ cup - Set aside for crumb topping: $\frac{1}{4}$ cup 3. **Step 1: Find total sugar before setting aside** Add brown and white sugar: $$\frac{3}{8} + \frac{1}{3} = \frac{3 \times 3}{8 \times 3} + \frac{1 \times 8}{3 \times 8} = \frac{9}{24} + \frac{8}{24} = \frac{17}{24}$$ 4. **Step 2: Subtract the sugar set aside for crumb topping** $$\frac{17}{24} - \frac{1}{4} = \frac{17}{24} - \frac{1 \times 6}{4 \times 6} = \frac{17}{24} - \frac{6}{24} = \frac{11}{24}$$ 5. **Answer:** The remaining sugar mixture used in the cake is $\frac{11}{24}$ cup. This matches one of the given options.