Answer:
younger sibling = 29 years
older sibling = 35 years
Explanation:
Let
x = younger sibling
y = older sibling
x + y = 64 (1)
The older sibling was born 6 years before their young sibling
x = y - 6 (2)
Substitute x = y - 6 into (1)
x + y = 64
y - 6 + y = 64
2y = 64 + 6
2y = 70
y = 70/2
y = 35 years
Substitute y = 35 into (2)
x = y - 6
x = 35 - 6
x = 29 years