Length of the slope is given as
[tex]L = 15 m[/tex]
also the inclination is given as
[tex]\theta = 30 degree[/tex]
now the horizontal displacement is let say "x"
now from geometry we can say
[tex]\frac{x}{L} = cos30[/tex]
[tex]x = L cos30[/tex]
now substitute all values in it
[tex]x = 15 * cos30[/tex]
[tex]x = 12.99 m[/tex]
so it will displace horizontally by 12.99 m