Answer:
If Eric sells boxes of cookies for $8 each, and Yolanda sells boxes of cookies for $10 each, and they made the same amount of money, then Eric sold 5 boxes.
Explanation:
To solve this problem, you must find the lowest common multiple of eight and ten. That would be 40, which is how much they both made. $40 / $8 per box = 5 boxes.
...And you don't need to know this, but Yolanda sold 4.