There are 83 students in Class A and Class B, 86 students in Class B and Class C, and 88 students in Class C and D. How many people are there in Class A and Class D?
甲班和乙班共83人，乙班和丙班共86人，丙班和丁班共88人，问甲班和丁班共多少人？
<gadget id="calculator">88 - 86</gadget>
<output>2</output>

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

<result>85</result>