PLEASE help with Geometry.

SOLVE FOR X.

Suzanne began a trip with 18 1/2 gallons of gas in the gas tank of her car if she hughes 17 3/4 gallons on the trip how many gallons does she have left once she finish the trip

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.

Table of values relation g values x, y 2,2 /3,5 /4,9 /5,13 which ordered pair is in g inverse? a(-2,2) b(-3,-5) c)4,9) d( 13,5)