If we assume that Nancy continues saving $2 from her allowance every 2 weeks, we know that it can be represented as:
2x10=20
This means at the end of 10 weeks, Nancy will have $20.
However, for Marco, as the weeks go up, He saved one more dollar. This can be represented as:
1+2+3+4+5+6+7+8+9+10=55
This means that at the end of 10 weeks, Marco will have $55.
At the end of 10 weeks, Marco will have saved more money than Nancy.