You did NOT list the interest rate so I can't calculate anything.
However, if you look at the attached formula,
principal = $650
n = 52
years = 8
-3/4 + 2 3/4
When dealing with a problem like this, it’s easiest to reorder the terms. So we’d say...
2 3/4-3/4=2
Then we’re really just subtracting 3/4 from the original number and our answer is 2.
Sara's results probably do have a higher mean, if we take into account how William is way more willing to pay 20 dollars. Honestly, I think you got your chosen answers right! Just my opinion, as someone inexperienced.
It’s equals 176 square cm