i need help on conversions

Many people drive extra to get low-priced gas at Costco. Bo's car needs 15 gal of gas. The nearby gas station is 3.50 dollars per gal, while Costco is 3.30 dollars per gal but requires driving an extra 18 miles (9 miles each way). Suppose driving costs about 35 cents per mile, considering gas, tires, oil, depreciation, etc. How much is saved by getting gas at Costco?

these types of questions really confuses me