an item is regularly priced at $63. justin bought it at a discount of 45% off the regular price. find out how much justin paid

Which graph represents an even function?

Two planes leave an airport at the same time, one flying east, the other flying west. the eastbound plane travels 20 mph slower. they are 1600 mi apart after 2 hr. find the speed of each plane.

How do you use the elimination method for this question? explain, because i really want to understand!