Here is the original item:
To make her ex-boyfriend Brad jealous, Georgia saved her money. To buy a
black dress that would turn men’s heads at the winter dance.
You chose to attach the infinitive phrase to the main clause in front, like this:
To make her ex-boyfriend Brad jealous, Georgia saved her
money;
to buy a black dress that would turn men’s heads at the winter dance.
Unfortunately, you cannot connect these two parts with a semicolon. Review the rules.