a)

You are driving up the hypotenuse of a triangle. 2.7 km = 2700 m.

sin(θ) = opposite/hypotenuse = 170/2700 = 0.063

θ = sin^{-1}(0.063) = 3.61° Convert to radians if needed.

b)

Let x = the additional distance continuing up the incline.

sin(θ) = 45/x

x = 45/sin(θ) = 45/(170/2700) = 714.7 m

Or you can do it by similar triangles

170/2700 = 45/x

x = 45(2700)/170