ANSWER: 110
EXPLANATION:
Let these five numbers be a, b, c, d and e.
Then "arithmetic means of 5 numbers is 100" implies
(a + b + c + d + e) / 5 = 100
>> a + b + c + d + e = 500
And "arithmetic means of 2 of these numbers (suppose a and b) is 85" implies
(a + b) / 2 = 85
>> a + b = 170
Using these two equations, we have
(a + b) + c + d + e = 500
>> (170) + c + d + e = 500
>> c + d + e = 500 - 170
>> c + d + e = 330
So "the mean of the other 3 numbers (c,d and e)" is
(c + d + e) / 3 = 330 / 3 = 110
