$12,000 is invested for 4 years at a simple interest rate of 1.5%. how much does the investment earn?

You didn't say if the 1.5% was per month, per 6 months, or per year. So, I'm just gonna put it all.
1.5% per month: The interest is $8640 and the amount is $20640.
1.5% per 6 months: The interest is $1440 and the amount is $13440.
1.5% per year: The interest is $720 and the amount is $12720.

Iagree that is the answer to the question