What the rule for the transformation is

Lorne subtracted 6x3 – 2x + 3 from –3x3 + 5x2 + 4x – 7. use the drop-down menus to identify the steps lorne used to find the difference.

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

To solve the system of equations below, pedro isolated the variable y in the first equation and then substituted it into the second equation. what was the resulting equation? { 5y=10x {x^2+y^2=36