As, sum of digits of 584 = 5 + 8 + 4 = 17
and sum of digits of 488 = 4 + 8 + 8 = 20
Similarly, sum of digits of 294 = 2 + 9 + 4 =15
∴ Sum of digits of 378 = 3 + 7 + 8 = 18
Here, difference of both are (20 - 17 ) = ( 18 - 15 ) = 3
Therefore ? = 378 is an answer.
