If we have to represent 4/5 - 1/5 in a number line, we should do this:
The result should be 3/5.
When we have to perform a substraction, we have to consider the signs of the terms.
In this case, we start from 4/5, which is a positive value.
Then, we have to substract 1/5 form 4/5.
To do that, we have to consider that substracting 1/5 is like adding a negative number. Then, the direction is the opposite to the increase of the line.
Then, we represent 1/5 to the left, substracting from 4/5.
The result is then 3/5, matching the result of the arithmetic operation.
Robbie did an addition of 4/5 and 1/5 instead of a substraction. She should have represented 1/5 to the left of 4/5 instead of the right.
