Mr. Hamm's salary has increased by 250% over the past 10 years. If his original salary was $28,000 per year, what is his current salary?

When you say this, I'm assuming he has gained this in total, not once a year:

2.50 (28000) + 28000

We can make it simpler:

3.50 (28000)

98000

Mr. Hamm now receives $98,000 a year