The head teacher led 50 students in Class 1, Grade 4 to plant trees. The teacher planted 5 trees, the boys planted 3 trees, and the girls planted 2 trees. A total of 120 trees were planted. How many more girls are there than boys in this class? ．
班主任老师带领四年级1班的50名同学栽树，老师一人栽了5棵，男生一人栽3棵，女生一人栽2棵，总共栽树120棵，那么这个班的女生比男生多了多少人．
<gadget id="calculator">155 - 120</gadget>
<output>35</output>

<gadget id="calculator">50 - 35</gadget>
<output>15</output>

<gadget id="calculator">35 - 15</gadget>
<output>20</output>

<result>20</result>