It's quite easy.

If the largest number of marbles in a bag is 47, then it will always be part of the largest sum.

i.e largest number + middle number = largest sum

So,

47 + middle number = 85

middle number = 85 - 47 = 38

Largest number + smallest number = second largest sum

47 + smallest number = 76
Smallest number = 76 - 47 = 29


Check this with the smallest sum

Smallest sum = smallest number + middle number

= 29 + 38
= 67

This matches the question's 67 exactly so we know our answer is correct.


The answer for this question is 29 (option 3)

In fact, to solve this question, the largest number in a bag ,47 is not even needed in the question.