Answer:
See image attached for complete answer
Explanation:
The attached image shows the calculation of probabilities for each branch
I believe it is self-explanatory
Since P(bus to shops) = 0.4, P(walk to shops ) = 1- 0.4 = 0.6
Since P(bus from shops) = 0.7, P(walk from shops) = 1- 0.7 = 0.3
The probabilities at the leaves of the tree(rightmost entries) show the combined probabilities of to and from
For example if she takes a bus to the shops and takes a bus from the shops, the combined probability = 0.4 x 0.7 = 0.28
If she walks to the shops and takes a bus from the shops the combined probability = 0.6 x 0.7 = 0.42
The other two probabilities can be computed the same way
The probability that she walks at least one way
= P(walking to shop) or P(walking from shop)
= sum of the probabilities in the yellow shaded boxes
= 0.12 + 0.42 + 0.18
= 0.72