It is understood that the prices of triple rooms and double rooms in Shenzhen Bay Hotel are: 200 yuan per person per day for triple rooms and 300 yuan per person per day for double rooms.

A: A: (1) Suppose there is a triple room and a double room.

100×3a+ 150×2b = 63003 a+2b = 50。

The solution is a = 8b = 13.

A: We rented eight triple rooms and 13 double rooms.

(2) According to the meaning of the question, y =100x+150 (50-x) =-50x+7500, (0≤x≤50, take integer points).

(3) Because -50 < 0, y decreases with the increase of x 。

Therefore, when x satisfies x3, 50? When x2 is an integer value, that is, x=48, the accommodation cost is the lowest.

At this time y =-50× 48+7500 = 5 100 < 6300.

A: the accommodation fee of 6300 yuan a day is not the lowest; If 48 people live in a triple room, the minimum cost is 5 100 yuan.