1. The problem asks to find the percentage of questions Ruby answered correctly on her English test. 2. The formula to find percentage is: $$\text{Percentage} = \left(\frac{\text{Number of correct answers}}{\text{Total number of questions}}\right) \times 100$$ 3. Ruby got 18 correct out of 20 questions, so substitute these values into the formula: $$\text{Percentage} = \left(\frac{18}{20}\right) \times 100$$ 4. Simplify the fraction: $$\frac{18}{20} = 0.9$$ 5. Multiply by 100 to get the percentage: $$0.9 \times 100 = 90$$ 6. Therefore, Ruby answered 90% of the questions correctly. 7. The correct answer is C. 90%