To make a part, Xiao Zhang uses (2/5) h, and Xiao Wang uses (3/10) h less than Xiao Wang, how much h does Xiao Wang use to make this part.
做一种零件，小张用(2/5)h，比小王少用(3/10)h，小王做这种零件要用多少h．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/5) + (3/10)</gadget>
<output>7/10 = around 0.7</output>

<result>7/10 = around 0.7</result>