Question 4771
The problem says that shift one production is 3 times shift two.

shift_one_production+shift_two_production=6400

since shift_one_production = 3* shift_two_production, we have

3* shift_two_production + shift_two_production = 6400

4*shift_two_production = 6400.

shift_two_production = 6400/4 = 1600

shift_one_production = 1600*3 = 4800.

You could have used 'x' instead of shift_one_production, the result would be the same.