Final answer:
Joe paid $1,260 in interest over 2 years.
Step-by-step explanation:
To calculate the amount of interest Joe paid in 2 years, we can use the formula: Interest = Principal * Rate * Time. In this case, the principal is $9,000, the rate is 7% (which is equivalent to 0.07), and the time is 2 years. Plugging these values into the formula gives: Interest = $9,000 * 0.07 * 2 = $1,260. Therefore, Joe paid $1,260 in interest over 2 years.