Answer:
x = 13 two-liter bottles
Explanation:
Since we're told that Erica spent more than $80, we'll need an inequality to solve.
We know that (cost of pizza * quantity of pizza) + (cost of soda * quantity of soda) > $80
If we allow p to represent the number of pizzas and b to represent the number of soda bottles, our equation is
4.99p + 1.99b > 80
Since we also know that she bough 11 pizzas, we can plug this in for p. Then, we'll simply have to solve for b:

We had to round the 12.618 up to 13 for two reasons:
- We cannot have a fraction of a soda bottle, so only whole numbers make sense
- A value of 12.6 for b would make the cost less than 80, but Erica knows that her cost was more than 80
We can check our answer by plugging in 13 for b and seeing whether the value from 1.99 * 13 + 4.99 * 11 is greater than 80
4.99(11) + 1.99(13) > 80
54.89 + 25.87 > 80
80.76 > 80