If "-" and "`xx`" signs as well as "7" and "3" are interchanged, then which of the one following is correct ?
A. `20 xx 1 - 7 = 3`
B. `1 xx 20 - 7 = 20`
C. `3-7 xx 1 = 20`
D. `20 - 3 xx 1 = 7`

Options

A. A
B. B
C. D
D. C

Answer

To solve the problem, we need to interchange the signs and numbers as specified in the question. The "-" sign will be replaced with "xx" (multiplication), and "7" will be replaced with "3" and vice versa. Let's analyze each option step by step.

### Step 1: Analyze Option A
**Original:** `20 xx 1 - 7 = 3`
**Interchanged:** `20 xx 1 - 3 = 7`

Now, let's calculate the left-hand side (LHS):
- LHS = `20 * 1 - 3`
- LHS = `20 - 3`
- LHS = `17`

Now, compare LHS with RHS:
- LHS (17) ≠ RHS (7)

**Conclusion:** Option A is incorrect.

### Step 2: Analyze Option B
**Original:** `1 xx 20 - 7 = 20`
**Interchanged:** `1 xx 20 - 3 = 7`

Now, let's calculate the LHS:
- LHS = `1 * 20 - 3`
- LHS = `20 - 3`
- LHS = `17`

Now, compare LHS with RHS:
- LHS (17) ≠ RHS (7)

**Conclusion:** Option B is incorrect.

### Step 3: Analyze Option C
**Original:** `3 - 7 xx 1 = 20`
**Interchanged:** `3 - 3 xx 1 = 20`

Now, let's calculate the LHS:
- LHS = `3 - 3 * 1`
- LHS = `3 - 3`
- LHS = `0`

Now, compare LHS with RHS:
- LHS (0) ≠ RHS (20)

**Conclusion:** Option C is incorrect.

### Step 4: Analyze Option D
**Original:** `20 - 3 xx 1 = 7`
**Interchanged:** `20 - 3 xx 1 = 7`

Now, let's calculate the LHS:
- LHS = `20 - 3 * 1`
- LHS = `20 - 3`
- LHS = `17`

Now, compare LHS with RHS:
- LHS (17) ≠ RHS (7)

**Conclusion:** Option D is incorrect.

### Final Conclusion
After analyzing all options, none of the options are correct based on the interchanged values and operations.