If x represents the number of hours Shelton worked, then the expression 10.25x shows how much Shelton is paid for these x hours ($10.25 for an hour).
After taxes, social security, and his health care plan were deducted he earned
10.25x - 0.21(10.25x).
This means that taxes, social security, and his health care plan form 21% (0.21 as decimal) from 10.25x.
Answer: 21%