Given is :
Let the total number of sparkling cans of water used in a day be =x
As mentioned, the family uses more than 15 cans each day so inequality becomes ,
![x>15](https://img.qammunity.org/2020/formulas/mathematics/middle-school/pd2vz54mxa3iksk8i0528m3ooulfhgc2uu.png)
As they buy cases of water with 24 cans in each case. So less than 1 case is used in a day.
Number of cans used in a day is more than 15, so approx number of cans used in 30 days will be =
As each case contains 24 cans, so the number of cases that will contain 450 cans will be,
cases. Rounding this off to nearest whole number, we get 19 cases.
Hence, the family buys around 19 cases of sparkling water in 30 days.