Which two signs should be interchanged to make the following equation correct?
`56 + 7 div 5xx3-2=21`

Options

A. A. `+ and ÷
B. B. `xx and -`
C. C.`div and -`
D. D. `xx and -`

Answer

To solve the equation `56 + 7 div 5 * 3 - 2 = 21` and determine which two signs should be interchanged to make it correct, we will follow these steps:

### Step 1: Understand the Original Equation
The original equation is:
\[ 56 + \frac{7}{5} \times 3 - 2 = 21 \]

### Step 2: Evaluate the Left-Hand Side (LHS)
Let's evaluate the LHS using the order of operations (BODMAS/BIDMAS):
1. Division first: \( \frac{7}{5} = 1.4 \)
2. Then multiplication: \( 1.4 \times 3 = 4.2 \)
3. Now substitute back into the equation:
\[ 56 + 4.2 - 2 \]

### Step 3: Perform Addition and Subtraction
Now, we perform the addition and subtraction:
1. \( 56 + 4.2 = 60.2 \)
2. \( 60.2 - 2 = 58.2 \)

So, the LHS evaluates to \( 58.2 \), which does not equal \( 21 \).

### Step 4: Identify the Signs to Interchange
We need to interchange two operations to make the equation correct. Let's try interchanging the addition (+) and division (div).

### Step 5: Rewrite the Equation with Interchanged Signs
After interchanging, the equation becomes:
\[ 56 \div 7 + 5 \times 3 - 2 \]

### Step 6: Evaluate the New Left-Hand Side
Now, let's evaluate this new LHS:
1. Division first: \( 56 \div 7 = 8 \)
2. Then multiplication: \( 5 \times 3 = 15 \)
3. Substitute back into the equation:
\[ 8 + 15 - 2 \]

### Step 7: Perform Addition and Subtraction Again
1. \( 8 + 15 = 23 \)
2. \( 23 - 2 = 21 \)

Now, the LHS equals \( 21 \), which matches the RHS.

### Conclusion
The two signs that should be interchanged to make the equation correct are addition (+) and division (div).

### Final Answer
Interchange: **Addition (+) and Division (div)**.

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