1. The problem involves comparing the heights of Billy and Aiza using the ruler markings. 2. Billy's head is at the 12 cm mark, and Aiza's head is at the 7 cm mark on the ruler. 3. To find the difference in their heights, subtract Aiza's height from Billy's height: $$12\text{ cm} - 7\text{ cm} = 5\text{ cm}$$. 4. This means Billy is 5 cm taller than Aiza. 5. If the ruler is scaled such that 1 cm on the ruler corresponds to 0.1 m in real height (since Billy is 1.8 m tall and his head aligns with 12 cm), then each cm represents $$\frac{1.8\text{ m}}{12} = 0.15\text{ m}$$. 6. Using this scale, Aiza's height is $$7 \times 0.15 = 1.05\text{ m}$$. 7. Therefore, Billy's height is 1.8 m and Aiza's height is approximately 1.05 m. 8. The difference in their heights in meters is $$1.8\text{ m} - 1.05\text{ m} = 0.75\text{ m}$$. Final answer: Billy is 1.8 m tall, Aiza is approximately 1.05 m tall, and Billy is 0.75 m taller than Aiza.