There are 10 essays, lets call them a,b,c,d,e,f,g,h,i, and j.

They are in pairs, i.e 'a' and 'b' together, 'c' and 'd' together and so on, making 5 pairs.

The teacher says she will ask 3 essays on the exam, of which we can write any 1.

However, she will only ask 1 essay from a pair. There is no possibility of her asking both the essays from the same pair.

If I skip pairs 'cd' and 'ij', which leaves me with 3 pairs of essays, what is the probability of essays from those two skipped pairs coming in the exam?

(I tried to explain this as simply as i could, sorry if it's not clear.)

Thank you!