I need to convert the units of the milk from milliliters to fluid ounces, since that is what Christine needs. I can use the fact that $1$ liter is $1000$ milliliters and $33.8$ fluid ounces. So, $1$ milliliter is $\frac{33.8}{1000} = 0.0338$ fluid ounces. That means $200$ milliliters is $200 \times 0.0338 = 6.76$ fluid ounces. Now I need to find how many bottles of $6.76$ fluid ounces I need to get at least $45$ fluid ounces. I can divide $45$ by $6.76$ to get an estimate of the number of bottles. I get $45 \div 6.76 \approx 6.65$. But I can't buy a fraction of a bottle, so I need to round up to the next whole number. The smallest number of bottles that Christine could buy is $7$. 
Christine must buy at least $45$ fluid ounces of milk at the store. The store only sells milk in $200$ milliliter bottles. If there are $33.8$ fluid ounces in $1$ liter, then what is the smallest number of bottles that Christine could buy?  (You may use a calculator on this problem.)