[填空题]
James goes on a cross-country bike ride which cd*voxyog*uy3 fmd t (*,aqm5/omprises of 8 km of flat mlt-m/y8o epbz-1l1 sterrain followed by 12 km of constant uphill sloping terrain. We know James can cycle at a speed of 24 km/hr m1 -zb/1tpll oys-m8e in flat terrain, however we don't know his speed on sloping uphill terrain, and therefore denote this by x km/hr.
1.Show his average speed over the entire ride, in terms of x, can be expressed as
S(x)=$\frac{60x}{x+36}$
2.Find $S^{−1}$(x).
3.Hence find the speed he needs cycle over the sloping uphill terrain in order to obtain an average speed of 20 km/hr for the whole ride. km/h
