To find the missing number in the equation __________ + 500 + 700 = 1,300, we can set up the equation as follows:
Let \( x \) be the missing number.
So, the equation becomes: \[ x + 500 + 700 = 1,300 \]
Now, combine 500 and 700: \[ x + 1,200 = 1,300 \]
Next, subtract 1,200 from both sides to solve for \( x \): \[ x = 1,300 - 1,200 \] \[ x = 100 \]
Therefore, the missing number is 100.