How to solve -3x+y=10 step by step

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.

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)

41/17 as a decimal rounded to the nearest hundredth