That is, the other two people need to pay 8-4=4 yuan for their free luggage.
1 person free luggage. If you pay, you need to pay 4÷2=2 yuan.
Then if all three people pay for free luggage, they should pay 2×3=6 yuan.
That is, if the luggage is paid in full, it should be minus 4+6= 10 yuan, which is 150 kg.
So each yuan can carry 150÷ 10= 15 yuan.
Each person can carry free baggage worth 2 yuan, that is, 15× 2 = 30kg.