In this case, since Malik bought a backyard shed for $3760, and pays $800, the remaining would be $2960. This amount is being paid $150 per month for 2 years. This means, 150 times 24 months is a total of $3600. From $2960, it became $3600. So the interest rate is annually is 20%. If compounded monthly, the rate is 18%. Hope this answers your question.