if the average ( arithmetic mean ) of x + 1 , x + 4 , and x + 7 is 0 , then x =
"( x + 1 + x + 4 + x + 7 ) / 3 = 0 = > 3 x + 12 = 0 = > x = - 4 answer a"
subtract(multiply(4, const_2), multiply(1, const_2))