In the statement the phrase the sum of can tell you that it is going to be an addition problem. So 8x ( eight times a number) would be added to the 15, 8x+15. Since its an addition problem the part where it says ' ... is seven', you know that it will all equal 7. So the answer would be 8x+15=7.
When you are doing probability with multiple things at once you have to multiply the probabilities of each asked number from each object together to get the probability of them both landing on those numbers
The large cup is best to buy. This is because it costs 11 cents per ounce for the medium cup and 11 cents for the large cup as well. You get almost double the amount for the same price with the large cup.
