Final answer:
To find the interest rate, use the formula I = P * r * t and solve for r. In this case, the interest rate is 8%.
Step-by-step explanation:
To find the interest rate, we can use the formula for simple interest: I = P * r * t, where I is the interest, P is the principal amount, r is the interest rate per year, and t is the time in years. In this case, the principal amount is $2000, the interest is $1280, and the time is 8 years.
Using the formula, we can rearrange it to solve for the interest rate:
r = I / (P * t)
Substituting the given values:
r = 1280 / (2000 * 8) = 0.08
Therefore, the interest rate is 8%.