Answer:the total amount of water used by the two households on that Saturday is 360 gallons
Explanation:
Let x represent the total amount of water used by the two households on that Saturday. On that Saturday, the ratio of the amount of water used by household A to the amount of water use by household B was 13 : 5. The total ratio is 13 + 5 = 18
The amount of water used by household A would be
13/18 × total amount of water.
The amount of water used by household B would be
5/18 × total amount of water.
Since household A used 260 gallons of water for that day, it means that
13/18 × x = 260
13x = 260×18 = 4680
x = 4680/13 = 360