Vanessa deposited money into a bank account that earned 1.25% simple interest each year. After 12 year, she had earned $5.00 in interest on the account.

Question

If no other money was deposited into or withdrawn from the account, how much was her initial deposit?

Answer 1

Interest = P*r*t, where P is principal, r is the rate as a decimal, and t is the number of years

so....

5 = P(.015)(12)
solve for P

A rather unrealistic question. You say that "no other money was deposited into or withdrawn from the account", so where does the annual interest go ?