Given that a student has failed in paper2 , the probability of failing in paper1 is 0.6.
First of all, it is a conditional probability.
and given that P(F1 ∣ F2) = 0.6 ,P(F1) =.3 ,P(F2) =.2
By conditional Probability
P(F1 ∩ F2) = P(F2) .P(F1 ∣ F2) = .2 * .6 =0.12
You can also solved this Qs by Other methods too but you need you to study Renormalization concept .Your soln is wrong due to this.
For Cp I recommend watch Harvard stat101 conditional probability lectures 4 and 5.