In the year $2010$, John's monthly salary was $\$3500$. John's monthly salary in $2010$ was $25\%$ more than it was in $2009$.
Calculate his monthly salary in $2009$.
Many of us debated the answer should be $\$2800$ as year $2010$ should be taken as $125\%$.
However, the answer given by the 7th grade teacher is $\$2625$.
What's your view on this question?
Let $S_{2009}$ be John's salary in $2009$ and $S_{2010}$ in salary in $2010$. What is given is that $$3500=S_{2010}=1.25 \times S_{2009}$$ So, dividing both sides by $1.25$ leads to $$ S_{2009}= \frac{3500}{1.25}=2800$$ and you are perfectly right.