Answer:
Smallest possible x = 98.
Explanation:
4312 = 2 * 2 * 2 * 7 * 7 * 11
56 = 2 *2 * 2 * 7
154 = 2 * 7 * 11
Because the HCF is 14:-
x = = 2 * 7 OR 2 * 7 * other prime number(s).
As there are 2 7's in the prime factors of 4312 there must also be another 7 in the prime factors of x.
x = 2 * 7 * 7 = 98.