Please helppp plisss

Kayla made observations about the sellin price of a new brand of coffee that sold in the three different sized bags she recorded those observations in the following table 6 is $2.10 8 is $2.80 and 16 is to $5.60 use the relationship to predict the cost of a 20oz bag of coffee.

Let f(x) = 5/x and g(x)=2x2+5x. what two numbers are not in the domain of f o g

How can writing phrases as algebraic expressions you solve problems?