Given that the advertising company had a setup fee of $80, this would mean that
Next, since it is stated that they add $4 for every advertisment, we let x as the number of advertisement, and this would mean that we add 4x to the equation that we initially had
Now, to write ordered pairs for the fees for 10, 20, 30, and 40 advertisements, we just have to substitute these values to the equation
x = 10
( 10, 120 )
x = 20
( 20, 160 )
x = 30