A candidate is required to answer 7 questions

We know that,

nCr

$=\frac{n !}{r !(n-r) !}$

No of questions in group A=6

No of questions in group B=6

According to the question,

The different ways in which the questions can be attempted are,

Hence, the number of different ways of doing questions,

= (6C2x6C5)+(6C3x6C4)+(6C4x6C3)+(6C5x6C2)

= (15×6)+(20×15)+(15×20)+(6×15)

=780