In a tree planting activity, the ratio of the number of trees planted between the sixth grade and the fifth grade is 8:5. It is known that the fifth grade planted 21 trees less than the sixth grade. How many trees are planted in total by the two grades?
在一次植树活动中，六年级与五年级植树棵数的比是8：5，已知五年级比六年级少植树21棵，两个年级一共植树多少棵？
<gadget id="calculator">8 - 5</gadget>
<output>3</output>

<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<gadget id="calculator">3 / 13</gadget>
<output>3/13 = around 0.230769</output>

<gadget id="calculator">21 / (3/13)</gadget>
<output>91</output>

<result>91</result>