During Arbor Day, Guangming Primary School organized three classes of sixth graders to plant trees together. Among them, the number of trees planted by class 1 is that of class 2 (9/8), the number of trees planted by class 3 is that of class 2 (7/8), the number of trees planted by class 1 is 90, how many trees are planted by class 3?
植树节时，光明小学组织六年级三个班学生共同植树．其中，一班植树棵数是二班的(9/8)，三班植树棵数是二班的(7/8)，一班学生植树90棵，三班植树多少棵？
<gadget id="calculator">9 / 8</gadget>
<output>9/8 = around 1.125</output>

<gadget id="calculator">90 / (9/8)</gadget>
<output>80</output>

<gadget id="calculator">7 / 8</gadget>
<output>7/8 = around 0.875</output>

<gadget id="calculator">80 * (7/8)</gadget>
<output>70</output>

<result>70</result>