Answer: 15 coins
Explanation:
Alex has friends = 12
He has total coins = 63
Now, if he want to add minimum number of coins in his coins for distribution,
The difference in the number of coin must be same or minimum,
The minimum difference between number of coins his friends can get = 1,
Minimum number of coin one person can get = 1,
Therefore, the order of coin that having minimum sum,
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
Total sum of this AP = 78
Thus, the minimum coins he can give all of his 12 friends = 78
Since, 78-63 = 15
⇒ The minimum number of additional coin = 15