Use Pythagorean theorem!
A^2 + B^2 = C^2
In this case, let's make A = the difference in height, and B= the difference in width.
Since you're looking for C, the distance between the two points, plug in the distance of the height and width! (Without worrying about C
A = 1-9 = -8
However, you can't have a negative height. So use absolute value to get A= 8
Then find the difference in width
B= 7- -2 = 9
Then plug in:
A^2 + B^2 = C^2
8^2 + 9^2 = C^2
145 = C^2
This can be confusing, but to get rid of the ^2 on C, you take the sqrt (square root) of both sides
C = sqrt (145)
Then use calculator
12.041
Round to tenth
12
Hope this helps!