Answer:
144 dollars
Step-by-step explanation:
We are told that:
Lewis and his sister both begin with a balance of zero dollars.
Now, for every 4 dollars that Lewis saves in his account, his sister saves 9 dollar.
Now, if Lewis has 64 dollars in his account, it means he saved 4 dollars for 64/4 times or 16 times.
Therefore his sister saved 9 dollars for 16 times too.
Thus, his sister saved: 16 × 9 = 144 dollars