I need to find te missing angle for this question

How do i do this activity, is appreciated

In which form is the following function written? y = - 2(x – 3)(x + 5)

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?