Answer:
12
Explanation:
The altitude divides the hypotenuse into parts using this proportion
6/n = n / 18 Cross multiply
n^2 = 6 * 18
n^2 = 108
n = sqrt(108)
n = sqrt(4 * 9 * 3)
n = 2*3 *sqrt(3)
n = 6*sqrt(3)
Now use Pythagoras to get m. m is the hypotenuse of the small triangle on the left
m^2 = n^2 + 6^2
m^2 = 6^2 *sqrt(3)^2 + 36
m^2 = 36*3 + 36
m^2 = 108 + 36
m^2 = 144
m = sqrt(144)
m = 12