Hello! This seems like you are missing some data in the question! We can start by figuring out the values we can create.
How far have you gone?
Traveled at 80.3 km/hour for 3.5 hours, and you want that answer in miles, and there are 1.61 km in every milefor the final calculation. Let's set up the unit conversion.
80.3 km/1 hour * 1 mile/1.61 km * 3.5 hours = ? miles
80.3 km/1 hour * 1 mile/1.61 km * 3.5 hours = ? miles (unit cancellation checks out)
80.3 km/1 hour * 1 mile/1.61 km * 3.5 hours = 174.57 miles
How much gas have you used?
Your car gets 22.6 miles/1 gallon and you have traveled 174.57 miles. We want our answer in gallons, so we can set our unit conversion up like this:
1 gallon/22.6 miles * 174.57 miles = ? gallons
1 gallon/22.6 miles * 174.57 miles = ? gallons (units cancel)
1 gallon/ 22.6 miles * 174.57 miles = 7.72 gallons
How much does that cost?
This is a complicated answer, because you don't have the data for it, because you could find out how much gas costs in Ireland in €⁄L and then convert that to $/gal or you could take the average price, in $/gal in Saint Louis and use that. If you set up those problems like I have above, you should be able to find the answers no problem.
Best of luck!