Answer:
46
Explanation:
Let a to d be number 1 to 4 respectively.
15 = (a + b + c + d) / 4
(a + b + c + d) = 60 ------> total sum of the 4 numbers
Since the sum of 3 numbers (assuming a to c) is 14,
Fourth number (d) = 60 - 14
= 46
That's how I would do it, hope this helps :)