[quote=PrecalcKid114;59688]need quick help! i dont understand these at all and i have a test tomorrow. damn summer school. anyways

A tourist walks n km at 4 km/h and then travels 2n km at 36 km/h by bus. Express the total traveling time t in hours as a function of n.

Answer is t(n) = 11n/36 i dont know how to get it though[\quote]

recall that

Let be the time the journey on foot takes

Let be the time the journey by bus takes

Let be the total time

Thus we have

For :

For :

Thus we have: