If an automobile travels 245 mi with a gas mileage of 21.5 mi/gal how many kilograms of CO are produced? Assume that the gasoline is composed of octane, C8H18 (l), whose density is 0.69 g/mL.

By now you have posted the balanced equation.

You can do this problem in English/American units (gallons, pounds, etc) and convert to Kg of CO2 (note your typo) at the end or you can go metric from the start. Its your choice. These unit conversions are a major part of the problem you have been assigned.

If you are taking chemistry you should be able to handle the math to determine the gallons of gas consumed. Volume times density gives the mass of octane consumed. This, in turn, gives you the mass (kg) of CO2 produced.

The conversions, the stoichiometry, etc often seem tedious to work through. Have patience, these are the type of problem you get in the real world. I have done hundreds (or maybe thousands) of them. Working these problems is like eating an elephant. How do you do that? ONE BITE AT A TIME! Keep working and you will get the correct answer.