What should come in place of '?'
$$6 \times 4 \times 3 = 436,$$
$$8 \times 4 \times ? = 468,$$
$$6 \times 9 \times 8 = 986,$$
The equation uses the middle number in the hundred's place, the rightmost number in the tenth's place and the left most letter in the unit's place. So, the number to be used in the place of the question mark is 6.