Need help with this question

You earn a 12% commission for every car you sell. how much is your commission if you sell a $23,000 car?

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827

Which sum or difference identity would you use to verify that cos (180° - q) = -cos q? a.) sin (a -b) = sin a cos b – cos a sin b b.) cos (a -b) = cos a cos b – sin a sin b c.) cos (a -b) = cos a cosb + sin a sin b d.) sin (a + b) = sin a cos b + cos a sin b