The number of third-grade students in a certain school is as follows: Class A and Class B have 83 students in total, Class B and Class C have 86 students in total, and Class C and Class D have 88 students in total. How many people are there in Class A and Class D?
某校三年级学生数如下：甲班和乙班共83人，乙班和丙班共86人，丙班和丁班共88人．甲班和丁班共几人？
<gadget id="calculator">88 - 86</gadget>
<output>2</output>

<gadget id="calculator">83 + 2</gadget>
<output>85</output>

<result>85</result>