Red sun hotel

Answer: Answer: ① We rent a triple room X and a double room Y.

3x+2y = 503×50x+2×70y = 15 10÷50%，

X = 8y = 13，

∴ 8 triple rooms and 13 double rooms;

② There are (50-x) people living in the double room.

According to the meaning of the question, y=[50x+70(50-x)]×50%.

That is, y =-10x+1750 (0 ≤ x < 50, x is an integer);

(3) Because the two rooms are just full, the value of x is a multiple of 3, and (50-x) is still a multiple of 2.

So some points on the image are: (0, 1750) (6, 1690) (12, 1630) (18,1570) (.

④ It is not the minimum cost, because y decreases with the increase of x, so the minimum cost is 1270 yuan when x=48.