if 7 and 9 are factors of 60 n , what is the minimum value of n ?
"60 n / 7 * 9 should be integer = > 2 * 2 * 3 * 5 * n / 7 * 3 * 3 = 2 * 2 * 5 * n / 21 must be an integer for this to be true n must multiple of 21 , thus min of n = 21 hence e"
lcm(7, 9)