Answer:
The cost of the old ball was $100.
Explanation:
The cost of the new ball = $300
The new ball has three times the price of his old ball.
So, let the price of the old ball be = x
As per situation, we get the equation:
![3x=300](https://img.qammunity.org/2020/formulas/mathematics/college/2twtyix0tpanywb2n4czd0h793hljufh70.png)
Dividing both sides by 3:
![(3x)/(3)= (300)/(3)](https://img.qammunity.org/2020/formulas/mathematics/college/smfel398wv801etnwtf8oebfhpq1q5qdxy.png)
=> x = 100
Hence, the cost of the old ball was $100.