I don't seem to understand this

Abank manager wants to encourage new customers to open accounts with principals of at least $2 comma 500. he decides to make a poster advertising a simple interest rate of 3%. what must the principal be if the bank manager also wants to advertise that one can earn $10 the first month? can the poster correctly say, "open an account of $2 comma 500 and earn at least $10 interest in 1 month! "?

On questions #8 and #9 don't mind my answers they're probably wrong.

Commission or salary: jill has a job offer. she is offered either $50 per day or ? 30 per day plus a commission of $3 for every plant she sells. how many plants does she need to sell to make the commission offer the best paying option?