Answer:
![Highway = 155\ miles](https://tex.z-dn.net/?f=Highway%20%3D%20155%5C%20miles)
![City = 130\ miles](https://tex.z-dn.net/?f=City%20%3D%20130%5C%20miles)
Step-by-step explanation:
Given
![Highway = 31mi/gallon](https://tex.z-dn.net/?f=Highway%20%3D%2031mi%2Fgallon)
![City = 26mi/gallon](https://tex.z-dn.net/?f=City%20%3D%2026mi%2Fgallon)
![Total\ Miles = 285](https://tex.z-dn.net/?f=Total%5C%20Miles%20%3D%20285)
![Total\ Gallons = 10](https://tex.z-dn.net/?f=Total%5C%20Gallons%20%3D%2010)
Required
Determine the number of miles driven on the highway and on the city
Represent the gallons used on highway with h and on city with c.
So, we have:
---- gallons used
and
--- distance travelled
In the first equation, make c the subject
![c = 10 - h](https://tex.z-dn.net/?f=c%20%3D%2010%20-%20h)
Substitute 10 - h for c in the second equation
![31h + 26c = 285](https://tex.z-dn.net/?f=31h%20%2B%2026c%20%3D%20285)
![31h + 26(10 - h) = 285](https://tex.z-dn.net/?f=31h%20%2B%2026%2810%20-%20h%29%20%3D%20285)
Open bracket
![31h + 260 - 26h = 285](https://tex.z-dn.net/?f=31h%20%2B%20260%20-%2026h%20%3D%20285)
Collect like terms
![31h - 26h = 285 - 260](https://tex.z-dn.net/?f=31h%20-%2026h%20%3D%20285%20-%20260)
![5h = 25](https://tex.z-dn.net/?f=5h%20%3D%2025)
Make h the subject
![h = \frac{25}{5}](https://tex.z-dn.net/?f=h%20%3D%20%5Cfrac%7B25%7D%7B5%7D)
![h = 5](https://tex.z-dn.net/?f=h%20%3D%205)
Substitute 5 for h in ![c = 10 - h](https://tex.z-dn.net/?f=c%20%3D%2010%20-%20h)
![c = 10 - 5](https://tex.z-dn.net/?f=c%20%3D%2010%20-%205)
![c = 5](https://tex.z-dn.net/?f=c%20%3D%205)
If on the highway, he travels 31 miles per gallon, then his distance on the highway is:
![Highway = 31 * 5](https://tex.z-dn.net/?f=Highway%20%3D%2031%20%2A%205)
![Highway = 155\ miles](https://tex.z-dn.net/?f=Highway%20%3D%20155%5C%20miles)
If in the highway, he travels 26 miles per gallon, then his distance on the highway is:
![City = 26 * 5](https://tex.z-dn.net/?f=City%20%3D%2026%20%2A%205)
![City = 130\ miles](https://tex.z-dn.net/?f=City%20%3D%20130%5C%20miles)