To celebrate Teacher's Day, the students hung some balloons in the classroom. Among them, there are 68 red balloons, 16 less than three times the number of purple balloons. How many purple balloons are there?
为庆祝教师节，同学们在教室里挂了一些气球，其中红气球有68个，比紫气球的3倍少16个，紫气球有多少个？
<gadget id="calculator">68 + 16</gadget>
<output>84</output>

<gadget id="calculator">84 / 3</gadget>
<output>28</output>

<result>28</result>