She can buy a maximum of 8 apples.
Step-by-step explanation:
Let x represent the number of apples that she wants to buy.
The grocery store sells apples for $1 each and mangos for $0.50 each.
If Gabriella decided to buy 13 mangos, it means that the cost of buying x apples and 13 mangoes is expressed as
x + 13 × 0.5 = x + 6.5
If she buy at least 19 apples, it means that
x + 13 ≥ 19
x ≥ 19 - 13
x ≥ 6
Gabriella has $15 to spend. It means that
x + 6.5 ≤ 15
x ≤ 15 - 6.5
x ≤ 8.5
Therefore, the maximum number of apples that she can buy is 8