There are 138 students in the sixth grade who subscribe to magazines, among which (5/6) students subscribe to "Science Pictorial", and (2/3) students subscribe to "King of Intelligence". How many students are ordered for both books?
六年级有138名学生订杂志，其中有(5/6)的学生订《科学画报》，有(2/3)的学生订《智力大王》．两种读物都订的有多少名学生？
<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(2/3) - 1</gadget>
<output>-1/3 = around -0.333333</output>

<gadget id="calculator">(5/6) + (-1/3)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">138 * (1/2)</gadget>
<output>69</output>

<result>69</result>