Skill: Balance subtraction equations

An equation is balanced when both sides have the same value. The equal sign means “has the same value as,” not just “the answer comes next.”

Solve:

$$725-300=400+\Box$$

1. Find the value of the left side. Subtract $300$ from $725$:

$$725-300=425$$

So the equation becomes:

$$425=400+\Box$$

2. Ask: “What number added to $400$ makes $425$?” Use a related addition fact or subtract:

$$425-400=25$$

3. Put $25$ in the box:

$$725-300=400+25$$

4. Check both sides:

$$725-300=425$$

and

$$400+25=425$$

Both sides equal $425$, so the equation is balanced. The missing number is $\boxed{25}$.