Mario received 0.40 in change from 20 when he bought tail mix. how many pounds of tail mix did mario buy? trail mix: $3.50 per pound

So making a simple equation helps to get all the information together

20 - 3.5X = 0.4

20 is the original. Minus the amount you paid for. equals the cash you got back

subtract 20 over

-3.5X=-19.6
Then divide both sides by -3.5
X=5.6

He bought 5.6 pounds 

The answer is 225 miles per 4.5 hours. hope this ; )