I have been trying to work this sum out for some time now, But I cant get a proper answer.

Heres the sum, my answer can be found below

A biathalon even involves running and cycling. Kim can cycle 30km/h faster than she can run. If Kim spends 48 minutes running and a third as much time again cycling in an event that covers a total distance of 60 km, how fast can she run?

Here is my answer:

Running speed = $\displaystyle x km/h$

cycling speed = $\displaystyle x + 30 km/h$

$\displaystyle \frac{48}{60} \times x+\frac{16}{60} \times (x+30)=60$

$\displaystyle x=48.75$

This is wrong because the book says the answer is 15 km/h

What am I doing wrong here?