Question 912465
Sana is twice as old as her youngest brother:<br/>

s = 2b<br/>

If the difference between their ages  is 15 years:<br/>
s = b + 15<br/>

Since we know the value of s is equal to 2b, we can substitute:<br/>

2b = b + 15<br/>
Then subtract b from each side:
2b = b + 15
-b&nbsp&nbsp&nbsp-b<br/>

b = 15<br/>

Therefore, the age of the little brother is 15 years.
And the age of Sana is 30.