A man invests a certain amount of money at 2% interest and $800 more than that amount in another account at 4% interest. At the end of one year he earned $112 in interest. How much money was invested in each account? Which of the following equations could be used to solve the problem?

OPTIONS:
0.02x + 0.04(800) = 112
0.02x + 0.04(x + 800) = 112
0.04x + 0.02(x + 800) = 112

Please don't just give me the answer, please explain how you GOT your answer. Thank you.