Bài 2:
Gọi đáy lớn ban đầu là a, đáy nhỏ ban đầu là b.
Theo đề bài, ta có hệ phương trình sau:
(a + b)/2 = 32,5
(a + 12 + b + 8)/2 = 32,5 + 90
Simplifying the equations, we have:
a + b = 65
a + b + 20 = 147,5
Subtracting the first equation from the second equation, we get:
20 = 82,5
This is not possible, so there is no solution for this problem. Therefore, we cannot calculate the area of the field.

Bài 3:
Gọi quãng đường từ A đến B là x.
Theo đề bài, ta có hệ phương trình sau:
x/2 + 5x + 3 = 28
Simplifying the equation, we have:
x/2 + 5x = 25
Multiplying both sides of the equation by 2, we get:
x + 10x = 50
Combining like terms, we have:
11x = 50
Dividing both sides of the equation by 11, we get:
x = 4.545
Therefore, the distance from A to B is approximately 4.545 km.

Bài 4:
Gọi hai số cần tìm là a và b.
Theo đề bài, ta có hệ phương trình sau:
a + b = 136,5
0,6a = 0,87b
Dividing both sides of the second equation by 0.6, we get:
a = 1.45b
Substituting the value of a in the first equation, we have:
1.45b + b = 136.5
Combining like terms, we have:
2.45b = 136.5
Dividing both sides of the equation by 2.45, we get:
b = 55.714
Substituting the value of b in the first equation, we have:
a + 55.714 = 136.5
Subtracting 55.714 from both sides of the equation, we get:
a = 80.786
Therefore, the two numbers are approximately 80.786 and 55.714.