Question 859722
Let x = number of girls



So there are 30-x boys



{{{2/3 = x/(30-x)}}}



{{{2(30-x) = 3x}}}



{{{60-2x = 3x}}}



{{{60 = 3x+2x}}}



{{{60 = 5x}}}



{{{60/5 = x}}}



{{{12 = x}}}



{{{x = 12}}}



There are 12 girls in the class.