Follow the Order of Operations to solve complicated problems.
Attempt to solve equations without writing down intermediate values. If you must write down values, keep as many digits or decimal places as you can. Better yet, use the memory locations in your calculator to store intermediate values.
NEVER round intermediate calculations. Only round the final answer.
Simple Interest: Don took out a $20,000 loan at 18% simple interest which resulted in a future value of $22,500. How many days was the loan held? Assume a year is 365.25 days.