#### Explanation:

Cost of one gallon of gas = $1.35 Cost of 20 gallons of gas = 1.35 * 20 =$27.00

#### Explanation:

The cost of gas per gallon is $$1.35$. Hence the cost of $20$gallons of gas $= 20 \setminus \times 1.35$$= 27$Hence the cost of filling a $20$-gallon tank is$$27$