1. **Problem:** Two similar triangles have bases 7 cm and 14 cm. Triangle A has area 20 cm². Find the area of triangle B. 2. **Formula:** Areas of similar triangles scale as the square of the ratio of corresponding sides. 3. **Step:** Calculate the scale factor for sides: $$\text{scale factor} = \frac{14}{7} = 2$$ 4. **Step:** Calculate the scale factor for areas: $$\text{area scale factor} = 2^2 = 4$$ 5. **Step:** Calculate area of triangle B: $$\text{Area}_B = 20 \times 4 = 80$$ 6. **Answer:** The area of triangle B is 80 cm².