11 more than y please help

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

When the solutions to each of the two equations below are graphed in the xy-coordinate plane, the graphs of the solutions intersect at two places. write the y-cordninates of the points of intersection in the boxes below in order from smallest to largest. y=2x y=x^2-3

Factor the polynomial expression x6 – x3 – 20