Well to solve these type of question it is very easy to make a tree diagram and then solve them. How ever i have done it here for you.
So basically we have to get a pen from the first box so its probability is 7 / 10.
Similarly, we have to get a crayon from the second box so its probability is 2 / 8.
Now by counting principle we can multiply the two probabilities so 7/10 * 1/4 which becomes equal to 7/40.
The answer to your question is : 15x - 3y
The sale price = 99(1 - 0.1)(1 - 0.25)(1 - 0.08) = 99 * 0.9 * 0.75 * 0.92 = $61.48
They are making the customer purchase more because they get more money and the customer gets 2 packs because they want buns for each of their hot dogs
0.00066233938 is what it equals
