There were originally 42 students in Class 51. After 3 boys were transferred in the new semester, the number of boys accounted for (5/9) of the whole class. How many girls are there?
五1班原有42人，新学期转入3个男生后，男生人数占全班人数的(5/9)．女生有多少人？
<gadget id="calculator">42 + 3</gadget>
<output>45</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">1 - (5/9)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">45 * (4/9)</gadget>
<output>20</output>

<result>20</result>