Given,
Mathematics paper has 20 questions of equal marks
and have three sections A,B&C, also A has 8 questions, B has 6 questions and C has 6 questions,
Now, if 4 questions from each section are selected,
then remaining 3 questions can be selected either in (1,1,1) or (3,0,0) or (2,1,0) {as we have already selected 4×3=12 questions}
So, the total ways will be=C58⋅C56⋅C56+C68C56⋅C46×2+C58⋅C66⋅C46×2+C48⋅C66⋅C56×2+C78⋅C46⋅C46
=56⋅6⋅6+28⋅6⋅15⋅2+56⋅15⋅2+70⋅6⋅2+8⋅15⋅15
=2016+5040+1680+840+1800=11376