it's simple:
[tex] {distance}^{2} = {(y2 - y1)}^{2} + {(x2 - x1)}^{2} [/tex]
[tex] {distance}^{2} = {(17 - 5)}^{2} + {(12 - 7)}^{2} \\ = {12}^{2} + {5 }^{2} = 144 + 25 = 169[/tex]
so taking the square root of both sides we find:
[tex]distance = \sqrt{169} = 13[/tex]
