Let the number of people in the first, second and third workshops be x, y and z respectively, and the total number of people is a.
Formula: y/a = 0.25;
(y-z)/y = 1/5;
(x-z)/z=3/ 10 .
Because the first workshop is 156, it is calculated that there are 144 people in the second workshop and 120 people in the third workshop, totaling 420 people.