Answer:
(-3x²- 9x+5) - (-2x²-4x +7)
= (-3x²- 9x²+5) (2x²+4x +7)
=-3x²-9x+5+2x²+4x-7
=-3x²+2x²-9x+4x+5-7
=-x²-5x-2
Now CHECK by substituting into the angles in your question, 8(17-10)=56 and 90-34=56, so x=10 and y=17, and they each make up the angle of 56 degrees