Solve the following problems: 1. 3.45 x ? = 3450 2. 3 x 7 = 4 x 6 - ? 3. 45.76 + 5.95 = ? 4. (3)/(4) - (5)/(12) = ?

To change 3.45 to 3450, the decimal point moves three places to the right.

Moving the decimal point one place to the right is multiplying by 10.
Moving it three places to the right is multiplying by $10 \times 10 \times 10 = 1000$.
So, $3.45 \times 1000 = 3450$.
The missing number is $\boxed{1000}$.

2.

The missing number is $\boxed{3}$.

3.

Align the decimal points.

The sum is $\boxed{51.71}$.

4.

The least common multiple of 4 and 12 is 12.

The difference is $\boxed{\frac{1}{3}}$.

5.

Divide 5 by 4: 1 with remainder 1.
Bring down 8, making 18. Divide 18 by 4: 4 with remainder 2.
Bring down 6, making 26. Divide 26 by 4: 6 with remainder 2.
Bring down 7, making 27. Divide 27 by 4: 6 with remainder 3.
So, $5867 \div 4 = 1466$ with a remainder of 3.

As a mixed number: $1466 \frac{3}{4}$
As a decimal: 1466.75 (since $\frac{3}{4} = 0.75$)
The result is $\boxed{1466.75}$.