Answer: [tex]-5\frac{3}{8}[/tex] tanks of gas
Step-by-step explanation:
Let the x be the number of tanks of gas, then
The amount of gas used by first car= [tex]1\frac{3}{4}x=\frac{7}{4}x[/tex]
The amount of gas used by second car= [tex]2\frac{1}{8}x=\frac{17}{8}x[/tex]
The amount of gas used by third car= [tex]1\frac{1}{2}x=\frac{3}{2}x[/tex]
Thus, the total change in the amount of gas for all three cars=[tex]\frac{7}{4}x+\frac{17}{8}x+\frac{3}{2}x[/tex]
[tex]=x(\frac{7}{4}+\frac{17}{8}+\frac{3}{2})\\\\=x(\frac{14+17+12}{8})\\\\=x(\frac{43}{8})\\=5\frac{3}{8}x[/tex]
Since, the amount of gas [tex]5\frac{3}{8}[/tex] tanks of gas is used for all three cars.
Therefore, the total amount would be negative .
hence, the answer is [tex]-5\frac{3}{8}[/tex] tanks of gas.
