Luis left a 20% tip on a $30.00 food bill. how much did he leave for the tip?

Which answer is the solution set to the inequality |x|< 9? a. x< -9 or x> 9 b. x> -9 and x< 9 c. x> -9 or x< 9 d. x< 9 and x< 9

F(x)= 4x g(x) =x-1 what is f(x) divided by g(x)

Can someone tell me if this is perpendicular? !