To find out how much sugar Lisa used for 256 fluid ounces of sweet tea, we first determine the ratio of sugar to fluid ounces from the initial information.
Lisa used 5 grams of sugar for 8 fluid ounces of sweet tea.
Now, let's calculate the amount of sugar used per fluid ounce:
\[ \text{Sugar per fluid ounce} = \frac{5 \text{ grams}}{8 \text{ fluid ounces}} = 0.625 \text{ grams per fluid ounce} \]
Next, we will multiply the amount of sugar per fluid ounce by the total fluid ounces of sweet tea she made last week (256 fluid ounces):
\[ \text{Total sugar for 256 fluid ounces} = 0.625 \text{ grams per fluid ounce} \times 256 \text{ fluid ounces} \]
Calculating this:
\[ 0.625 \times 256 = 160 \text{ grams} \]
Therefore, Lisa used 160 grams of sugar to make 256 fluid ounces of sweet tea last week.