Answer: $307.5
Explanation:
Here, Elena's aunt bought her a $150 savings bond when she was born.
That is, the initial amount = $150
And, When Elena is 20 year old, the bond will have earned 105% in interest.
Therefore, The bond be worth when Elena is 20 years old,

⇒A= $307.5
Therefore, after 20 years the the bond worth $307.5.