The students planted trees. The fourth grade planted 56 trees, the fifth grade planted 28 trees three times less than the fourth grade, and how many fewer trees were planted in the fourth grade than in the fifth grade?
同学们栽树，四年级栽了56棵，五年级栽的棵树比四年级的3倍少28棵，四年级比五年级少栽多少棵？
<gadget id="calculator">56 * 3</gadget>
<output>168</output>

<gadget id="calculator">168 - 28 - 56</gadget>
<output>84</output>

<result>84</result>