How do i solve the system y=x+2, y-x=8 using the substitution method?

The last time i bought this product , it cost $20.00 but it looks like it cost 29. 60 today? what is the increase

X-intercept=-5 y-intercept=2 the equation of the line is

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?