.write 803,000,000 in scientific notation.

The amount spent on food and drink by 20 customers is shown below what is the modal amount spent and the median amount spent? 40 25 8 36 18 15 24 27 43 9 12 19 22 34 31 20 26 19 17 28

Lines a and b are perpendicular. if the slope of line a is 3, what is the slope of line b?

Ireally don't understand this, i'm really an idiot but i want to know how to figure this out. !