After David receives a 20% raise in salary, his new salary is $27000. What was his old salary?

Taylor--

If the new salary of 27000 is 20% (or 0.20) MORE than his old salary, then

we can say his new salary is 120% of his old salary (the original 100% plus the extra 20%). Therefore, letting his old salary be denoted as x, we have:

1.2x = 27000

x = 27000/1.2 = 22500.

Therefore, David's original salary was $22,500.

(And easy way to check this? 20% of 22500 is 4500. Adding that to 22500: (22500 + 4500 = 27000). )