if 2 : 9 : : x : 18 , then find the value of x
"explanation : treat 2 : 9 as 2 / 9 and x : 18 as x / 18 , treat : : as = so we get 2 / 9 = x / 18 = > 9 x = 36 = > x = 4 option c"
divide(add(multiply(9, 2), 9), 18)