The third-grade students of the experimental primary school adopted 30 trees in the park, the fourth-grade students adopted 10 fewer trees than the third-grade ones, and the fifth-grade students adopted three times as many trees as the fourth-grade ones. How many trees did the fifth-grade students adopt?
实验小学三年级学生在公园里认养了30棵树木，四年级认养的树木比三年级的2倍少10棵，五年级学生认养的树木是四年级的3倍，五年级学生认养了多少棵？
<gadget id="calculator">30 * 2</gadget>
<output>60</output>

<gadget id="calculator">60 - 10</gadget>
<output>50</output>

<gadget id="calculator">50 * 3</gadget>
<output>150</output>

<result>150</result>