Answer: The required number of gallons of gas that is left is [tex]\dfrac{3}{4}.[/tex]
Step-by-step explanation: Given that Susan began a trip with [tex]18\dfrac{1}{2}[/tex] gallons of gas in the gas tank of her car. If she used [tex]17\dfrac{3}{4}[/tex] gallons on the trip.
We are to find the number of gallons that are left when she finished the trip.
According to the given information, we have
number of gallons of gas that Susan has in her car is
[tex]N_g=18\dfrac{1}{2}=\dfrac{37}{2}[/tex]
and the number of gallons of gas that she used on the trip is given by
[tex]N_u=17\dfrac{3}{4}=\dfrac{71}{4}.[/tex]
Therefore, the number of gallons of gas that is left after finishing the trip is
[tex]N\\\\=N_g-N_u\\\\=\dfrac{37}{2}-\dfrac{71}{4}\\\\\\=\dfrac{74-71}{4}\\\\\\=\dfrac{3}{4}.[/tex]
Thus, the required number of gallons of gas that is left is [tex]\dfrac{3}{4}.[/tex]
