Question

Susie is trying to calculate 7−(−3) . She uses the subtraction algorithm and finds that the answer is 10. She is confused about why her answer is bigger than either of her original numbers since she is subtracting. How could a number-line model be connected to the expression 7−(−3) to help Susie understand why her answer of 10 is correct?(1 point) Responses On a number line, start at point 7. Then move 3 in the negative direction. On a number line, start at point 7. Then move 3 in the negative direction. On a number line, find the distance from −3 to 7. On a number line, find the distance from negative 3 to 7. On a number line, start at point −3. Then move 7 in the positive direction. On a number line, start at point negative 3 . Then move 7 in the positive direction. On a number line, look at the distance from point 3 to point 7.

Answer 1

To help Susie understand why \( 7 - (-3) \) equals \( 10 \) using a number line model, the best response is:

**On a number line, start at point \(-3\). Then move \(7\) in the positive direction.**

Here's the reasoning:

1. Starting at \(-3\) means you're at the position of the negative number.
2. When you subtract a negative number, it is equivalent to adding the positive version of that number. So moving \(7\) units in the positive direction from \(-3\) would lead you to \(7\).
3. Thus, starting from \(-3\) and moving \(7\) units to the right will lead you to the point \(10\), which clearly illustrates that \(7 - (-3) = 10\).

This way, Susie can visualize and understand that subtracting a negative number effectively increases the value, which is why her answer is greater than either of the original numbers.