if the average ( arithmetic mean ) of a and b is 100 , and c – a = 120 , what is the average of b and c ?
"a + b / 2 = 100 = > a + b = 200 a = c - 120 . . . sub this value c - 120 + b = 200 = > c + b = 320 = > c + b / 2 = 160 answer : c"
subtract(multiply(120, const_2), multiply(100, const_2))