(5a-28):(3a+28)= 1:2

10a-56=3a+28

7a=84

a= 12

A pile of apples is 60kg and B pile is 36kg.

(2) Solution: Suppose the annual income ratio is 4x:3x and the annual expenditure ratio is 18y: 13y.

4x- 18y=720

3x- 13y=720

X=5y, substituting 4x- 18y=720, we get:

20y- 18y=720

Y=360, so X = 5 * 360 = 1800.

Therefore, the annual income of the two brothers is 7,200 yuan and 5,400 yuan respectively.

(3) Solution: If the large bottle weighs 4x kg, the small bottle weighs (2.7-4x) kg.

Then 2.7-4x = 2x, then x = 0.45.

So the big bottle was originally loaded with 1.8 kg, and the small bottle was originally loaded with 0.9 kg.

(4) Solution: If the unit price of big basket apples is 2x, then the unit price of small basket apples is 3x; The weight of the big basket of apples is 2y, and the weight of the small basket of apples is 3y.

Y = 20 from 2y+3y= 100, so the weight of the big apple is 40 kg, and that of the small apple is 60 kg.

Then (40 * 2x+60 * 3x)/ 100 = 4.4,

So x = 22/ 13.

So the unit price of the big apple is 44/ 13 and 66/ 13.

(5) Solution: Let the unit price of apples be 6x and that of pears be 5x; The weight of an apple is 2y, and that of a pear is 3y.

So there are 6x * 2y+5x * 3y = 18.

Get12xy+15xy =18.

So xy = 2/3.

Bought apples 12xy = 12 * 2/3 = 8 yuan, bought pears 18-8 = 10 yuan.