To find this answer, you would need to find how many miles 1 gallon of gas will take them. To find this, you would do 290÷8=36.25. So with this information, you will be able to find out how much gas it would take to travel 400 miles. You would do 400÷36.25=11.03. 11.03 would be how many gallons of gas is used to travel 400 miles. Hope this helps! :)