Question 1150617
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<pre>

Let x be the number of students in the class.


Then the number of girls is 0.6x, while the number of boys is 0.4x.


The difference is


    0.6x - 0.4x = 18, 

i.e.

    0.2x        = 18

       x        = 18/0.2 = 180/2 = 90.    <U>ANSWER</U>
</pre>

Solved.