Answer:
6/7 ≈ 85.7%
Step-by-step explanation:
The probability that a 0 was transmitted and received is 0.5·0.9 = 0.45.
The probability that a 1 was transmitted and a 0 received is 0.5·0.15 = 0.075.
Then the probability that a 0 was received is 0.45 +0.075 = 0.525.
The probability of interest is ...
p(0 transmitted | 0 received) = p(0 transmitted & received)/p(0 received)
= 0.45/0.525 = 6/7 ≈ 85.7%