The question doesn't have any requirement. I'll calculate the water Halle has left for lunch after drinking the rest.
Answer:
Halle has 250 ml of water for lunch
Explanation:
Fractions and Proportions
Fractions often express ratios between partial and total measures. In this context, 1/4 means 1 part out of 4 parts.
Halle goes to school with 1 liter of water in a bottle, she drinks 1/4 of the bottle before school starts. The bottle now has 3/4 of a liter of water
Halle drinks 2/3 of it before lunch, it means that the bottle has 1/3 of 3/4 left of the water. Since 1/3*3/4 = 1/4. That is the fraction of water still present in the bottle.
Since 1 liter is 1000 ml, Halle has 1/4*1000= 250 ml of water for lunch