① 7x+8y=380
② 10x+6y=380
Substitute the deformed y=(380-7x)/8 from ① into ②;
10x+6{(380-7x)/8 }=380
The solution is x=20.
Substitute x=20 into ① to get y=30.
A: The purchase prices of souvenirs A and B are 20 yuan and 30 yuan respectively.
(2) Solution: If X souvenirs A are purchased, then souvenir B is a 40-x inequality group:
① 20x+30(40-x)≤900
② 5x+7(40-x) ≥2 16
Solution: 30≤x≤32
So x can be 30,365,438+0,32.
When x=30, the profit is 220 yuan.
When x=3 1, the profit is 2 18 yuan.
When x=32, the profit is 2 16 yuan.
So x takes 30 hours or the most profit.
So when x=30, y= 10.
So we should buy 30 A-class souvenirs and 10 B-class souvenirs. Now we can get the biggest profit and the biggest value is 220 yuan.