Two events are said to be Disjoint or Mutually Exclusive if the two events can not happen at the same time.For example when we throw a die getting an even number is disjoint to getting an odd number.
I.e Probability(A∩B)=0
Let me explain this concept through venn diagram.
Pr[A∪B]=0.7, Pr[A]=0.25
Since events are Disjoint
Pr[A∩B]=0
Pr[A∪B]=Pr[A] + Pr[B]
0.7=0.25 +Pr[B]
0.7-0.25=Pr[B]
⇒Pr[B]=0.45=45/100=9/20
Now events are said to be independent if Pr[A and B]=Pr[A] ×Pr[B]
Events are said to be independent if occurrence of one is not affected by occurrence of other.For example getting multiple of 2 as one event and getting multiple of 3 as second event when we throw a die.
Pr[A∪B]=0.7, Pr[A]=0.25
Pr[A∪B]= Pr[A]+ Pr[B]-Pr[A∩B]
But Pr[A∩B]= Pr[A] ×Pr[B]
⇒Pr[A∪B]= Pr[A]+ Pr[B]- Pr[A] ×Pr[B]
⇒0.7=0.25+p-0.25×p
⇒0.7-0.25=p- 0.25 p
⇒0.45=0.75 p
⇒p= 0.45/0.75
⇒p =3/5
