Question #1: He eliminated 1 of the 3 choices. So the probability of getting correct answer is 1/2.
Question #2: He eliminated 1 of the 3 choices. So the probability of getting correct answer is 1/2.
For Question #3-5: The probability of getting correct answer is 1/3 and getting incorrect it 2/3.
He should get at least 2 out of 3 correctly answered. The probability would be :-
P(at least 2 correct out of 3) = P(exactly 2 correct) + P(all 3 correct)
![Probability=C(3,2)*((1)/(3) )^(2) *((2)/(3) ) + C(3,3)*((1)/(3) )^(3) \\\\ Probability=3*((1)/(9)) *((2)/(3) ) + 1*((1)/(27) ) \\\\ Probability=(6)/(27)+(1)/(27) \\\\ Probability=(6+1)/(27)=(7)/(27)](https://img.qammunity.org/2019/formulas/mathematics/high-school/mvj4uftneihnukvaiwtctb8zxiwzk8f0q5.png)
Combined probability would be =
![(1)/(2) *(1)/(2)* (7)/(27) =(7)/(108)](https://img.qammunity.org/2019/formulas/mathematics/high-school/ooevvujvuzb5a6t4mm2j7y3w2265pkkkw4.png)