Verified answer

the vertical component of acceleration is a sin 30 =

4.3 sin 30 = 2.15 m/s/s

if the elevation change is 340 m, then the length of the run (the hypotenuse of the triangle) is 340/sin30 = 680 m

to find the time to reach the bottom, use the equation of motion:

y(t)=y0+v0t+1/2at^2

let's assume the top of the ski run is at y0=0, we are told that the initial speed is zero, v0=0, and a=4.3 m/s/s

therefore

680=1/2 a t^2 or t=sart[1360/4.3] = 17.8s