Because the payment for the first shopping is less than the second shopping, the first shopping is less: 820/2=4 10 yuan.

820*0。 9=738 yuan, more than 728 yuan, indicating that the second time is not between 200 and 500.

Let x be the first time and y the second time.

1) I'm not in 200 yuan for the first time.

X+Y=820

X+500*0 .9+(Y-500)*0 .8=728

Solution: x =110; Y=7 10

2) Between 200 and 500 for the first time,

X+Y=820

0。 9X+500*0 .9+(Y-500)*0 .8=728

Solution: x = 220Y=600