Mr. Zhang bought a football for 33 yuan and a basketball for 39 yuan with 100 yuan. How much should the salesperson give Mr. Zhang?
张老师用100元钱买了一个价钱33元的足球和一个39元的篮球．营业员应该找给张老师多少元？
<gadget id="calculator">33 + 39</gadget>
<output>72</output>

<gadget id="calculator">100 - 72</gadget>
<output>28</output>

<result>28</result>