For a group of saplings, if male and female students are planted together, each person needs to plant 8 saplings on average; if only girls are planted, 10 saplings need to be planted on average. If only boys are allowed to plant, how many trees do they need to plant on average?
一批树苗，如果让男女学生一起栽，平均每人需栽8棵；如果只让女生栽，平均需栽10棵．如果只让男生栽，平均每人需栽多少棵？
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/8) - (1/10)</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">1 / (1/40)</gadget>
<output>40</output>

<result>40</result>