Cho hình chữ nhật ABCD có các cạnh AB, CD là hai cạnh đối diện nhau (O). Các đường cao AD, BE, CF từ điểm H. Gọi O là trung điểm cạnh AB. Tính độ dài các đoạn thẳng? AE = AC - AB; AD = AC - ME; AC = AE + AD

To solve the problem with rectangle ABCD and the heights AD, BE, CF from point H, we need to clarify the relationships between the lengths provided.

### Given
- Rectangle ABCD
- O is the midpoint of AB
- Relationships:
1. \( AE = AC - AB \)
2. \( AD = AC - ME \)
3. \( AC = AE + AD \)

### Breakdown

1. **From the first relationship:**
\[
AE = AC - AB
\]
This indicates that AE is the difference between the total length AC (the length of the rectangle) and the length AB (the width).

2. **From the second relationship:**
\[
AD = AC - ME
\]
Here, AD is expressed in relation to ME, which is not explicitly defined but could represent a specific midpoint or reference point in the rectangle.

3. **From the third relationship:**
\[
AC = AE + AD
\]
This clarifies that the total length AC is composed of the segments AE and AD.

### Calculating Sizes
To find the specific lengths, you can set values for AB (width) and AC (length). For example, let:
- \( AB = x \)
- \( AC = y \)

You can express the lengths based on those values:
- \( AE = y - x \)
- Use the relationships to also compute AD:
\[
AD = y - ME
\]

### Conclusion
With specific values of \( AB \) and \( AC \), you can substitute to find \( AE \) and \( AD \). If those values are hypothetical or theoretical, you can illustrate the concept without exact numbers. To progress further or calculate actual lengths, additional context or numerical values would be necessary.

Would you like to define specific lengths for AB and AC to proceed with calculations?