a. Chiều rộng của hình chữ nhật là \(x - 4\) (m)

b. Phương trình biểu thị sự kiện là: \(x - 4 < x\)

Simplifying the inequality, we get: \(-4 < 0\)

Since this inequality is always true, the event "The width is 4m less than the length" is always true.

To calculate the area of the rectangle, we use the formula: Area = Length x Width

Area = \(x \times (x - 4)\)

Area = \(x^2 - 4x\)

Given that the perimeter of the rectangle is 64m, we have:

\(2(x + x - 4) = 64\)

\(4x - 8 = 64\)

\(4x = 72\)

\(x = 18\)

Therefore, the length of the rectangle is 18m and the width is \(18 - 4 = 14\)m.

The area of the rectangle is \(18 \times 14 = 252\)m².