Answer:
[tex]\huge\boxed{15.3 \ \text{gallons}}[/tex]
Step-by-step explanation:
We know that Chang drove 420 miles on 18 gallons of gas.
This can be represented as a ratio, [tex]\frac{\text{miles}}{\text{gallons of gas}}[/tex].
[tex]\frac{420}{18}[/tex]
We can also represent 357 miles over an unknown gas quantity as a ratio.
[tex]\frac{357}{x}[/tex]
Since he uses a proportional amount of gas to his miles, we can set these two proportions equal to each other to find the value of x.
[tex]\frac{420}{18} = \frac{357}{x}[/tex]
To find the value of x, we can use the cross products property.
[tex]357 \cdot 18 = 6426\\\\6426 \div 420 = 15.3[/tex]
So he needs 15.3 gallons of gas to drive 357 miles.
Hope this helped!
