Answer: By the 8th week.
Explanation:
Let the time that matteo and luca have the same amount of money be represented by x.
The information given in the question can be formed into an equation as:
400 - 10x = 200 + 15x
Collect like terms
400 - 200 = 15x + 10x
200 = 25x
x = 200/25
x = 8
Matteo and Luca will have the same amount of money by the 8th week.