Replace each * by the correct digit in each of the following:

$\begin{matrix} & 6 & 5 & 0 & \ast \ - & \ast & 0 & \ast & 5 \ \hline & 4 & \ast & 5 & 7 \ \hline \end{matrix}$

$\begin{matrix} & 6 & 5 & 0 & \ast \ - & \ast & 0 & \ast & 5 \ \hline & 4 & \ast & 5 & 7 \ \hline \end{matrix}$

Units column: * - 5 = 7. Since this requires borrowing, * + 10 - 5 = 7, which gives * = 2. (Borrow 1 from tens)

Tens column: After borrowing, 0 - 1 - * = 5 requires further borrowing. So, 10 + 0 - 1 - * = 5, which gives * = 4. (Borrow 1 from hundreds)

Hundreds column: After borrowing, 5 - 1 - 0 = 4. So, the * in the result = 4.

Thousands column: 6 - * = 4, which gives * = 2.

Hence, the completed subtraction is:

$\begin{matrix} & 6 & 5 & 0 & 2 \ - & 2 & 0 & 4 & 5 \ \hline & 4 & 4 & 5 & 7 \ \hline \end{matrix}$

Verification: 6502 - 2045 = 4457.