The correct option is B 30
Let the number of boys and girls participating in sports be 3x and 2x respectively.
Then, 3x=15 or x=5.
So, number of girls participating in sports =2x=10.
Number of students not participating in sports =60−(15+10)=35.
Let number of boys not participating in sports be y.
Then, number of girls not participating in sports =(35−y).
Therefore (35−y)=y+5⇔2y=30⇔y=15.
So, number of girls not participating in sports =(35−15)=20.
Hence, total number of girls in the class =(10+20)=30.