15:3 in simplest form

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?

F(x)=5/6x+3 which of the following is true

Perry observes the opposite parallel walls of a room in how many lines do the plains containing the walls intersect