Concept:
In age-related questions, the difference in ages between two persons always remains constant.
To determine who is oldest, we must compare the present ages of A, B, and C.
Step 1: Checking Statement (I).
Given:
\[
10 \text{ years ago A was 5 years older than B}
\]
So,
\[
(A-10)=(B-10)+5
\]
\[
A=B+5
\]
Thus, A is 5 years older than B.
But there is no relation with C.
So, Statement (I) alone is not sufficient.
Step 2: Checking Statement (II).
Given:
\[
7 \text{ years from now B will be 8 years younger than C}
\]
So,
\[
(B+7)=(C+7)-8
\]
\[
B=C-8
\]
\[
C=B+8
\]
Thus, C is 8 years older than B.
But there is no relation with A.
So, Statement (II) alone is not sufficient.
Step 3: Checking both statements together.
From Statement (I):
\[
A=B+5
\]
From Statement (II):
\[
C=B+8
\]
Comparing:
\[
C=B+8 > A=B+5
\]
Thus:
\[
C>A>B
\]
So, C is oldest.
Hence, both statements together are sufficient, but neither alone is sufficient.