G.C.E.O-Level Maths Problem

G.C.E.O-Level Maths Problem
This is one of the question from the papaer in 1984
One hundred office workers use various combinations of travel by bus,train and car to reach their offices.of these one hundred workers,42 use buses,43 use cars and 66 use trains; 18 use both bus and train but not car,and 23 use train and car but not bus.There are no workers who use bus and car but not train.Every worker uses at least one of bus,train and car/
Denoting by x the number of workers who use all three means of transport.And Calculate x