For you to cover 222miles you will need about 35 tanks. You can get this by first finding out how many miles one tank can cover which is 57 divided by 9 getting 6.3miles. Then, finding how many 6.3miles are in 222 miles which is 222 divided by 6.3.
You will need 24.66 gal. of gas to go 222 mi. @ 9 mpg. 9mpg x 57 gal. = 513 miles possible for a full tank. 222 mi. / 9 mpg = 24.66 So to answer your question; just under a half tank... 24.66 gallons of gas.