if the average ( arithmetic mean ) of x and y is 60 , and z – x = 80 , what is the average of y and z ?
"x + y / 2 = 60 = > x + y = 120 x = z - 80 . . . sub this value z - 80 + y = 120 = > z + y = 200 = > z + y / 2 = 100 answer : a"
subtract(multiply(80, const_2), multiply(60, const_2))