What is the inverse function of this function

f(x)=4x

Frank owns a $141,000 home, for which he has a 30-year mortgage in the amount of $700 a month. once he has paid off mortgage, how much will he have paid in investment? a. $111,000 b. $109,000 c. $120,000 d. $141,000

If the tip varies directly with the number of guest which equation represents between the tip,t, and the number of guest,g?

Is the number 128.439 a rational number