If x people process 15 screws every day, then (20-x) people process 20 nuts every day.

15x 1

————— = —————

20(20 x)2

15x 1

————— = —————

400-20x 2

(15x) (2) = (400-20x) (1) (using cross multiplication)

30x = 400-20x

50x = 400

x = 8

Therefore, eight people should be arranged to process the screws, so that each screw can be equipped with two nuts after processing.