Below (after the reminder) is the answer to the Problem 2 of the lesson Some logic problems (the topic Miscellaneous word problems
of the section Word problems in this site).
Problem 2 formulation (reminder)
A carpenter, a plumber, and an engineer, whose names are Alex, Bob and Charlie, are flying from San Francisco to New York.
From their conversation in the plane it is revealed that
a) Alex and the engineer are going to work at a construction site;
b) the carpenter and Charlie live in Concord;
c) Bob is younger than the plumber;
d) Charlie is older than the engineer.
What are the names of the engineer and the carpenter?
Alex is a carpenter.
Bob is an engineer.
Charlie is a plumber.