A math application problem in the first grade can be listed as an equivalence relation and equation, that is, the city department store can engage in promotional activities, and the shopping does not exceed 200 yuan, and there is no discount. We assume that 1 shopping item needs X yuan without discount, and the second shopping item needs Y yuan without discount.

( 1-0. 1)x= 134

x= 1340/9

x= 149

500*0.9+(y-500)*0.8=466

y=520

520+ 149=669 yuan, then this person's two purchases are worth 669 yuan if they are not discounted.

2) 669- 134-466=69 yuan saves 69 yuan in this activity.

3) 500*0.9+ 169*0.8=585.2 yuan134+466-585.2 =14.8 yuan.

Therefore, it will be more economical if this person combines the money purchased twice to buy the same item.