Pythagorean theorem..
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[tex]{\huge{\underbrace{\bf{\pink{Answer}}}}}[/tex]
Length of missing leg = 12 km
Using Pythagoras theorem
a² = 15² - 9²
a = √ 225 - 49
a = √144
a = 12 km
HOPE IT HELPS..
(Hypotenuse)² = (Base)²+ (Perpendicular)²
Taking, Hypotenuse As H
Base As B
Perpendicular As P
_________________________
H²= B²+ P²
[tex]15 {}^{2} = 9 {}^{2} + p {}^{2} \\ \\ p {}^{2} = 15 {}^{2} + 9 {}^{2} \\ \\ p {}^{2} = 225 - 81 \\ \\p {}^{2} = 144 \\ \\ p = \sqrt{144} \\ \\ p = 12[/tex]