Find c. round to the nearest tenth

Combined megan and kelly worked 60 hours.kelly worked twice as many hours as megan.how many hours did they each worked?

Which coefficient matrix represents a system of linear equations that has a unique solution ? options in photo*

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