We had 8 apples, then we ate 5, how much apples we have now?
1. "we" is a noun.
2. "had" expresses a relation of belonging.
3. "8 apples" is what belongs to "we". Where "8" is a number and "apple" is a unit of calculation.
4. "then" is a sign that consequent events take place after an event of belonging.
5. "ate" corresponds to arithmentic operation of subtracting relating to belonging
6. "how much" means we should apply some unknown arithmetic operation
Basing on this information it is easily to form an equation 8 - 5 = z, which is the description of our task in time. In fact, solution is to identify 3 time points, and what links them (in this case, it is a relation between "we" and "apples").
A man has a wolf, a goat, and a cabbage. He must cross a river with the two animals and the cabbage. There is a rowing boat, in which he can take only one thing with him at a time. If, however, the wolf and the goat are left alone, the wolf will eat the goat. If the goat and the cabbage are left alone, the goat will eat the cabbage. How can the man get across the river with the two animals and the cabbage?
1. "man" is a noun.
2. "has" expresses belonging.
3. "wolf", "goat", and "cabbage" belongs to "man"
4. "he" indicates "man"
5. "cross" means passing something entirely
6. "river" means place
7. "cross a river" means passing from one bank to another
8. "with two animals and the cabbage" indicates what he has
9. "a rowing boat" could cross a river
10. "in which he can take only one thing with him at a time" means there is two place, for him and one thing.
10a. "a rowing boat, in which he can take" means a belonging inside a boat.
10b. "at a time" means one time point.
11. "If, however, the wolf and the goat are left alone, the wolf will eat the goat" refers to a rule
11a. The man, the wolf, the goat, and the cabbage could take place either on one of river banks, or inside a boat.
11b. "are left alone" means participants take place in one of these places.
11c. "the wolf eat the goat" means destructing of the goat
11d. "however" is only for accentuating
12. "If the goat and the cabbage are left alone, the goat will eat the cabbage" refers to another rule (see explanation of the previous item).
13. "How can the man get across the river" means at the beginning the man with all stuff is located at one bank, and in the end he should be at another.
Solution is, in fact, is just trying imaginably to move a man with one thing in a boat from one bank to another bank, and judge what will happen according to rules. If one of rule is applied, as soon as we moved the man with something to the boat, we roll back and try another variant.
This is quite simple examples. You can see that to solve any such example computer need to know a lot of implicit information which seems "evident" for us.