To determine the maximum number of packages (p) Emma can buy, we need to subtract the amounts she has spent and needs to set aside from her total budget.
Emma has $26 and she spent $12.81 on a book, so she has 26 - 12.81 = $13.19 remaining.
Additionally, she needs to set aside $10.00 for a lunch outing, so she has 13.19 - 10.00 = $3.19 remaining.
Each package of stickers costs $0.42, so we can divide the remaining budget by the cost of each package to find the maximum number of packages Emma can buy.
p = 3.19 / 0.42 ≈ 7.6
Since Emma cannot buy a fraction of a package, the maximum number of packages she can buy is 7.
Therefore, the correct response is "p≤7" which means p is less than or equal to 7.