Sanxin Primary School planted 90 trees, of which (2/5) were planted by the sixth grade, and (1/3) were planted by the fifth grade. How many trees did the two grades plant in total? (Comprehensive formula must be listed)
三新小学小学植了90棵树，其中(2/5)是六年级植的，(1/3)是五年级植的．两个年级一共植树多少棵？(必须列综合算式解决)
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(2/5) + (1/3)</gadget>
<output>11/15 = around 0.733333</output>

<gadget id="calculator">90 * (11/15)</gadget>
<output>66</output>

<result>66</result>