Answer:
1. Both Dan and Tess are correct.
Tess:
0.15 * 24.50 = 3.675
24.5 - 3.675 = 20.825
0.1 * 20.825 = 2.0825
20.825 + 2.0825 = 22.9075
Dan:
0.85 * 24.50 = 20.825
20.825 * 1.1 = 22.9075
Both Dan and Tess used methods that provided the correct answer. Both methods follow the same path, but Dan's method simply took less steps since he used percentages that would take out the correct number, unlike Tess' percentages which would give you the number that you would then need to take out.
2. First, convert Amy's and Mike's numbers to a decimal of the whole so it is easier to compare the numbers.
13% = 0.13 of the whole
Dan has 0.14 of the whole
0.5/6 = 0.083.. of the whole
Dan used the greatest amount of milk, using 0.14 of the 6 gallon container.
3.
2p + 12 = 58 | Create an equation to show the prices relations
2p = 46 | Take out the price of the concert ticket to leave us with the passes.
p = 23 | Divide by 2 to find the cost of each pass.
4.
x ≤ (18 - 6.5 - 5.75)/1.15
18 - 6.50 = 11.5 | Take out the price of the notebook from the total.
11.5 - 5.75 = 5.75 | Take out the amount of money that she wishes to save.
5.75 / 1.15 = 5 | Divide by the price of each candy to find the max amount that she can buy.
Andrea has enough money to buy up to 5 candy bars.
x ≤ 5
apples left. 
of it.
apples. So there isn't any difference when he ate 