a. A car travels a distance of 112 km at an average speed of 70 km/h. it then travels a further 60 km at an average speed of 50 km/h. Calculate, for the entire journey, the total time taken.

b. if  \(\frac{x}{y}\) = 2  and  \(\frac{y}{z}\) = 3, find the value of  \(\frac{ x + y}{y + z }\)