Y=x+3over 8 proportional or nonproportional

How far could you drive on 50 gallons of gas

Write the expression 7x^3-28xy^2 as the product of 3 factors

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?