We will have the following:
His speed on the return (r) trio was 4mph faster than his speed in the first trip (o), so:
![r=o+4](https://img.qammunity.org/2023/formulas/mathematics/college/6jtr2r1ew44bst3oe23gbrc1ibvbir00uq.png)
Then, we have that speed times distance equals time, and distance is equal to time over speed. Thus:
![6h(\frac{x}{\text{hours}})=4h(\frac{x+4}{\text{hours}})](https://img.qammunity.org/2023/formulas/mathematics/college/oq32aqbjwp2n4kizfda9lklic5dab9ny75.png)
Then, we have:
![6x=4x+16\Rightarrow2x=16](https://img.qammunity.org/2023/formulas/mathematics/college/zli0rek514o6fvyivyt7sy4t28yy75xeg6.png)
![\Rightarrow x=8](https://img.qammunity.org/2023/formulas/mathematics/college/ositdjvtrvyi9rq1pgajzkialewiyblos5.png)
So, the initial speed was of 8mph.
Then we deternine the distance:
![d=(8mi/h)(6h)\Rightarrow d=48mi](https://img.qammunity.org/2023/formulas/mathematics/college/8waqyarur04a6o21q4m0v2889xhza9t0xs.png)
So, the two cities are 48 miles apart.