In 2000 the average cost for a gallon of gasoline was 1.40 in 2007 the average cost for a gallon of gasoline is 2.60 what is the percent of increase rounded to the nearest whole number

Umm... if in 2000 it was 1.40 and in 2007 it was 2.60, you subtract the two ie 2.60 -1.40 and you will get 1.2
Then, take 1.2 and divide it by 1.40 and then multiply by 100

hope you got it :))