You can put this solution on YOUR website!
There are a couple of things here. I think they meant that the first 30,000 of a person's income is to be taxed at 2%, and if the person earned more than 30,000, only the amount over the 30,000 is to be taxed at 5%. The other thing is, 900 is not 2% of the 30,000. In other words, you didn't subtract 2% off the first 30,000.
Since we got the first piece of the piecewise function, let's nail down the second part. If the person earned more than 30,000, then the difference between what they earned and the 30,000 (AKA, (x - 30,000)) is the one taxed at 5%. So far, we have
. Remember that T(x) is the amount collected. We can't forget that they did collect 2% of the first 30,000. That's 600. So, the function is actually
Once you simplify that, you'll end up with
for income x > 30,000.