If `513xx21=63xx3xx`______, then then number in the blank space is:

Options

A. 28
B. 63
C. 67
D. 21

Answer

To solve the equation \( 513 \times 21 = 63 \times 3 \times \_\_\_\_ \), we need to find the value that fills in the blank space.

### Step-by-step Solution:

1. **Calculate \( 513 \times 21 \)**:
\[ 513 \times 21 = 10773 \]

2. **Set up the equation**:
We know from the problem statement that:
\[ 10773 = 63 \times 3 \times \_\_\_\_ \]

3. **Calculate \( 63 \times 3 \)**:
\[ 63 \times 3 = 189 \]

4. **Substitute back into the equation**:
Now we can rewrite the equation as:
\[ 10773 = 189 \times \_\_\_\_ \]

5. **Solve for the blank space**:
To find the value of the blank space, we divide \( 10773 \) by \( 189 \):
\[ \_\_\_\_ = \frac{10773}{189} \]

6. **Perform the division**:
\[ \_\_\_\_ = 57 \]

Thus, the number in the blank space is \( 57 \).

### Final Answer:
The number in the blank space is **57**.