1. We start with Bottle A containing 1.5 litres of water and Bottle B containing 100 millilitres of water. 2. Convert 1.5 litres to millilitres because we need to work in the same units: 1 litre = 1000 ml, so $$1.5 = 1.5 \times 1000 = 1500 \text{ ml}$$ 3. Let $x$ be the amount of water (in millilitres) poured from Bottle A to Bottle B. 4. After pouring, Bottle A will have $$1500 - x$$ ml, and Bottle B will have $$100 + x$$ ml. 5. According to the problem, both bottles contain the same amount of water after pouring. Therefore, set the equal amounts: $$1500 - x = 100 + x$$ 6. Solve for $x$: $$1500 - x = 100 + x$$ $$1500 - 100 = x + x$$ $$1400 = 2x$$ $$x = \frac{1400}{2} = 700$$ 7. So, 700 millilitres of water are poured from Bottle A into Bottle B.