Why is 1.71x10^7 written in standard form

The sum of two numbers is 12 and their difference is 18 what are the two numbers

An object is translated by (x + 4, y - 2). if one point in the image has the coordinates (5, -3), what would be the coordinates of its pre-image? (9, -5) (1, -5) (9, -1) (1, -1)

For the chance to be team captain, the numbers 1-30 are put in a hat and you get two chances to pick a number, without replacement. which formula correctly shows how to find the probability that you choose the number 1 and then 2?