Answer: Never because Aislyn cannot catch up if they make the same amount of money per day.
Explanation:
Assume that the day they will have the same amount of money is x.
The amount that Xander will have on that day is:
= 15 + 4x
The amount that Aislyn will have on that day is:
= 10 + 4x
Equate the two fractions:
15 + 4x = 10 + 4x
15 - 10 + 4x = 4x
5 = 4x - 4x
5 = 0x
What this means is that they will never have the same amount of money because they are increasing by the same amount so Aislyn will never catch up.