Answer: 1.3
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Work Shown:
The two points we have are
and

Apply the distance formula

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A shortcut is possible by subtracting the y coordinates of the two points, and making the result positive through the use of absolute value.
So we either say
|y1-y2| = |1.2-2.5| = |-1.3| = 1.3
or,
|y2 - y1| = |2.5 - 1.2| = |1.3| = 1.3
We get the same result. This shortcut is valid because the x coordinates of both points are the same.