Final answer:
Evan's Social Security contribution is 6% of his monthly salary of $2,800, which equates to $168. Therefore, the correct answer is (a) $168.
Step-by-step explanation:
The subject of this problem is mathematics, specifically dealing with percentages and basic income calculations. Evan's Social Security contribution is calculated by taking 6% of his monthly salary. To calculate 6% of $2,800, you multiply $2,800 by 0.06:
0.06 × $2,800 = $168
Therefore, Evan pays $168 for Social Security each month. The correct answer to the question is option (a) $168.