Shara borrowed money from her brother 6 months ago. She returned $10 per month to her brother. Currently, she was able to return half of the money she borrowed. How much will she still owe her brother 4 months from now? Let's be accurate as possible.
For 6 months, Shara was able to return $10 x 6 = $60 to her brother. Since she already returned half of the money, then this means she currently owes her brother $60. Four months from now, she will be able to pay an additional $10 x 4 = $40. Thus, she will still owe her brother $60 - $40 = $20 four months from now.
The answer: 20.