1. **State the problem:** We have 50 customers, and 45 of them ordered tacos. We want to find what percentage of the customers ordered tacos. 2. **Explain the double number line:** The bottom line represents the number of customers (0 to 50), and the top line represents the percentage (0 to 100%). The marker at 45 on the bottom corresponds to some percentage on the top line. 3. **Set up the proportion:** The percentage of customers who ordered tacos is given by the formula: $$\text{Percentage} = \frac{\text{Number who ordered tacos}}{\text{Total customers}} \times 100$$ 4. **Substitute the values:** $$\text{Percentage} = \frac{45}{50} \times 100$$ 5. **Simplify the fraction:** $$\frac{45}{50} = \frac{\cancel{45}}{\cancel{50}} = \frac{9}{10}$$ 6. **Calculate the percentage:** $$\frac{9}{10} \times 100 = 90$$ 7. **Interpretation:** 90% of the customers ordered tacos. **Final answer:** $$\boxed{90\%}$$