1. The problem is to find 20% of 90. 2. To find a percentage of a number, use the formula: $$\text{Percentage of a number} = \frac{\text{percentage}}{100} \times \text{number}$$ 3. Here, the percentage is 20 and the number is 90. 4. Substitute the values into the formula: $$\frac{20}{100} \times 90$$ 5. Simplify the fraction: $$0.2 \times 90$$ 6. Multiply: $$0.2 \times 90 = 18$$ 7. Therefore, 20% of 90 is 18.