This question depends on which question we are attempting at first ->
Say it start with question 1 then question 2:-
question 1 is wrong -> amout =0 -> probality=$0.2$
question 1 is correct and question 2 is wrong -> amount =100 ->probability =$0.8*0.5=0.4$
both question 1 and 2 are correct -> amount =$300$ -> probablity =$0.8*0.5=0.4$
So expected amont if he start with question 1-> $0*0.2+100*0.4+300*0.4=160$
Say it start with question 2 then question 1:-
question 2 is wrong -> amout =0 -> probality=$0.5$
question 2 is correct and question 1 is wrong -> amount =200 ->probability =$0.2*0.5=0.1$
both question 1 and 2 are correct -> amount =$300$ -> probablity =$0.8*0.5=0.4$
So expected amont if he start with question 1-> $0*0.5+200*0.1+300*0.4=140$
So he has better chance of gettiing more money if he choose question 1 first then question 2 which will fetch him 160 ruppes .
Now if we assume selection of question is random then ,
Selecting question no 1 first fetch us expected 160 ruppes with probability 0.5.
Selecting question no 2 first will fetch us expected 140 ruppes with probabilily 0.5 .
So ,Expected value we get = 0.5*160+0.5*140=150 ruppes .