Answer:
Annual water footprint for a typical American in m3 − 2×365 m3
Explanation:
We need the annual water footprint for a typical American first. Then, if each American was to reduce his or her daily water use by 2 m3, this would mean they would reduce his or her annual water use by 365×2 m3, since there are 365 days in a year, and this is the quantity that one needs to substract from the given annual water footprint for a typical American, also measured in m3.