Answer: So the plant without water has a 0.6 chance of living. with water has a 0.7, so a 0.1 increase of chance if the neighbor comes.
the probability that the neighbor to water the plant is of 0.86.
Then the probability of the plant to live is 0.6 + 0.1*0.86 = 0.686.
So the plant have a 68.6% probability to live