How to solve system of equation by elimination

This is done by getting each equation to have one term that is the opposite of the other. For instance, if the first equation has a 3x, the second should have a -3x. If the equations do not already have this, you must multiply one or both of the equations by a number to get them to match. 

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .