Let the number of ice-cream serving the sisters can buy be "s".
Each serving is $2.80, so the cost of "s" ice-creams will be:
This cost cannot exceed 10 dollars.
10 dollars is the maximum.
So, we can say that "2.80s" is equal to or less than 10.
We write it in inequality notation:
Solving for "s":
So, the logical solution is that the 5 sisters can buy 3 ice-cream servings with their budget.