In each of the following questions if the interchanges are made in signs and numbers, which one of the four equations would be correct?
Given interchanges: Signs: + and `xx` and numbers 4 and 5

Options

A. `5 xx 4 + 20 = 40`
B. `5 xx 4 + 20 = 85`
C. `5 xx 4 + 20 = 104`
D. `5 xx 4 + 20 = 95`

Explanation

To solve the problem, we need to interchange the signs and numbers as specified:

1. Interchange the signs:
- Replace `+` with `×` (multiplication)
- Replace `×` with `+` (addition)

2. Interchange the numbers:
- Replace `4` with `5`
- Replace `5` with `4`

Now, let's analyze each of the four options given in the question to see which one becomes correct after these interchanges.

### Option 1:
**Original Equation:** 5 × 4 + 20 = 40

**After Interchange:**
- Replace `5` with `4`
- Replace `4` with `5`
- Replace `+` with `×`

**New Equation:** 4 × 5 × 20 = 40

**Calculating the Left-Hand Side (LHS):**
- 4 × 5 = 20
- 20 × 20 = 400

**So, LHS = 400, and RHS = 40.**
This is **not correct**.

### Option 2:
**Original Equation:** 5 × 4 + 20 = 85

**After Interchange:**
- Replace `5` with `4`
- Replace `4` with `5`
- Replace `+` with `×`

**New Equation:** 4 × 5 × 20 = 85

**Calculating the Left-Hand Side (LHS):**
- 4 × 5 = 20
- 20 × 20 = 400

**So, LHS = 400, and RHS = 85.**
This is **not correct**.

### Option 3:
**Original Equation:** 5 × 4 + 20 = 104

**After Interchange:**
- Replace `5` with `4`
- Replace `4` with `5`
- Replace `+` with `×`

**New Equation:** 4 × 5 × 20 = 104

**Calculating the Left-Hand Side (LHS):**
- 4 × 5 = 20
- 20 × 20 = 400

**So, LHS = 400, and RHS = 104.**
This is **not correct**.

### Option 4:
**Original Equation:** 5 × 4 + 20 = 100

**After Interchange:**
- Replace `5` with `4`
- Replace `4` with `5`
- Replace `+` with `×`

**New Equation:** 4 × 5 × 20 = 100

**Calculating the Left-Hand Side (LHS):**
- 4 × 5 = 20
- 20 × 20 = 400

**So, LHS = 400, and RHS = 100.**
This is **not correct**.

### Conclusion:
None of the options seem to be correct after the interchanges. However, based on the video transcript, it seems that option 3 was mentioned as the correct answer, but all calculations show that it does not satisfy the equality.