Junior high school math problems help solve the whole process of solving problems. Thank you.

Solution: (1) If the price is increased by X yuan per kilogram, the daily sales will be reduced by 20 kilograms.

( 10+X)(500-20X)=6000

X^2- 15X+50=0

X 1=5，X2= 10，

But the requirement of the topic is to make customers get benefits, so the price should be kept at a minimum.

So we should give up 10 and take 5.

The price per kilogram should be increased by 5 yuan.

(2) If the price per kilogram is increased by X yuan, the daily sales volume will be reduced by 20X kilograms.

( 10+X)(500-20X)= 5000-200 X+500 X-20X？

=-20x？ +300x+500

=-x？ + 15x+25

=-(x- 15/2)？ +( 15/2)? +25

==-(x- 15/2)？ + 137.5≥ 137.5

Therefore, when X= 15/2=7.5, the profit of shopping malls is the largest.