Answer:
a. 0.04
b. 0.0136
c. 0.2364
Step-by-step explanation:
a. P(fails both the first and second test)
=P(fails the first test) × P(fails second test)
= (1-P(pass on the first try)) × (1-P(fails on the first try will pass on the second try))
=(1-0.75) × (1-0.84) =0.04
b. P(Fail three times in a row)
= P(fails both the first and second test) × P(fails third test)
=0.04 × (1-P(fails the first and second test will pass the third time))
=0.04 × (1-0.66) = 0.0136
c. P(Require at least two tries)
=P(fails on the first try will pass on the second try) + P(fails the first and second test will pass the third time)
= ( P(fails the first test) × P(passes second test) )+( P(fails both the first and second test)  × P(passes third test) )
= (0.25 × 0.84) + (0.04 × 0.66)
= 0.2364