The number of hours a certain type of battery will last is distributed normally with a mean of 500 minutes. The standard deviation is 50 minutes. Out of 240 batteries tested, how many batteries would you expect to still be working after 580 minutes?

It will be a whole number.

Look, when you want to do something like put it like x^2. x2 could mean x² or x₂. so to clear confusion, know the notation. to find the product multiply the x's and you get -8x and the y's and you get 6y. since it's all being multiplied it is just -8x6y, or answer a. although the better answer is -48xy(combining -8 and 6) because you should multiply constants whenever you can.