Please, please, please, help if you could show work too that would be amazing !!

Which expression can be used to determine the slope of the line that passes through the points -6, three and one, -9

Liz is shipping a package to her friend.the maximum weight of a medium flat-rate box is 20 pounds,including the box which weighs 6 ounces.write and solve an inequality to describe the possible weight ,w, of the contents that liz will ship to her friend if she must use a medium flat-rate box.

With number 11 ( show how you got the answer)