What states that when you add zero to any number the sum is that number

Which of the following would represent the sum of 3 consecutive integers if x is the first integer?

If f(x) =3x-2 and g(x) =2x+1 fins (f+ g) (x)

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