Answer:
![y = 15.5](https://img.qammunity.org/2021/formulas/mathematics/college/ri6cjgy3ijhd0l80yxhqkadgh7s5535lk5.png)
Explanation:
Given
![Total\ Distance = 20km](https://img.qammunity.org/2021/formulas/mathematics/college/cjkbndnwom5qhrm3senmorcw6r2jfyzo6g.png)
![Walks\ Hours= (3)/(2)\ hours](https://img.qammunity.org/2021/formulas/mathematics/college/uuofxyun97eftztybcxg49q7pupxmvujhx.png)
![Walks\ Rate = (3km)/(1\ hour)](https://img.qammunity.org/2021/formulas/mathematics/college/fkzcwed005j5lscznpg022bn8yecnlj05b.png)
Required
Determine the distance (y) covered by his car
First, we calculate the distance walked.
This is calculated as follows;
![Distance = Walk\ Hours * Walk\ Rate](https://img.qammunity.org/2021/formulas/mathematics/college/58dttip01w8okv0vvm4ynug2btzw20uai6.png)
![Distance = (3)/(2)\ hours * (3km)/(1\ hour)](https://img.qammunity.org/2021/formulas/mathematics/college/al9rm1nrstp3xdighbunbwpz02w5f0tcdf.png)
![Distance = (3)/(2)* 3km](https://img.qammunity.org/2021/formulas/mathematics/college/r2c328kqgeru8ggiijyt1l214um6hgtu1q.png)
![Distance = (3* 3km)/(2)](https://img.qammunity.org/2021/formulas/mathematics/college/fu3qwehglzksqsq8wrxfw0g5x2qofazfud.png)
![Distance = (9km)/(2)](https://img.qammunity.org/2021/formulas/mathematics/college/ps67bm6ot5o01pzba7kjuhq4eql392tc9y.png)
![Distance = 4.5km](https://img.qammunity.org/2021/formulas/mathematics/college/rsl1xxyp9yd9er7nq2179n3sbfooz11qdd.png)
This means that he walked 4.5 km
The total distance can be expressed as a sum of distance covered while walking and distance covered by car.
i.e.
![Walk + Car = Total](https://img.qammunity.org/2021/formulas/mathematics/college/qjaym9wr7cnyxnacp9f8zn5fqr8dqpjeau.png)
Make Car the subject
![Car = Total - Walk](https://img.qammunity.org/2021/formulas/mathematics/college/f17zsidukfzz6dlf8e5h55ayq29ezulddi.png)
This gives
![y = 20 - 4.5](https://img.qammunity.org/2021/formulas/mathematics/college/qoiv9rac3gajbd7y852cl877iehx2by44l.png)
![y = 15.5](https://img.qammunity.org/2021/formulas/mathematics/college/ri6cjgy3ijhd0l80yxhqkadgh7s5535lk5.png)
Hence, his car travelled 15.5km