When is it best to solve for a system of equations using graphing?

Me #1 using vocabulary words, including the word “congruent”, state why the measure of angle d is 120 degrees. #2 what is the measure of angle e and why?

Mary beth used the mapping rule to find the coordinates of a point that had been rotated 90° counterclockwise around the origin. examine the steps to determine whether she made an error. m (3, –6) is rotated 90° counterclockwise. (x, y) → (–y, x) 1. switch the x- and y-coordinates: (6, –3) 2. multiply the new x-coordinate by –1: (6(–1), –3) 3. simplify: (–6, –3) .

I'm confused on this could anyone me and show me what i need to do to solve it.