I need some help please help please

Which expression is equivalent to the expression shown?

Complete the solution of the equation. find the value of y when x equals to 6 4x+y=20

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