I just did a practice psat because im in 10th grade, and i made a 1290. Is that good? And how can i get better, and increase my math score?

Little's law can be applied to any part of the store, such as a particular department or the checkout lines. the store owner determines that, during business hours, approximately 84 shoppers per hour make a purchase and each of these shoppers spend an average of 5 minutes in the checkout line. at any time during business hours, about how many shoppers, on average, are waiting in the checkout line to make a purchase at the good deals store?