Class A buys a fountain pen for 20 yuan each, and class B buys a ballpoint pen for 16 yuan each. After the two classes purchased the same quantity, they found that the total price difference was 80 yuan after comparison. How many pieces are purchased by Classes A and B?
甲班购买钢笔每支20元，乙班购买圆珠笔每支16元．两班购买相同的数量后，经过比较发现总价相差80元．甲乙两班购买数量各是多少支？
<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<gadget id="calculator">80 / 4 / 4</gadget>
<output>5</output>

<result>5</result>