the amount of time a certain brand of light bulb lasts is normally distribued with a
mean of 1600 hours and a standard deviation of 55 hours. using the empirical rule,
what percentage of light bulbs last between 1490 hours and 1710 hours?

The correct answer is 7

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.