Please answer these questions fast.

Q21. In Figure 12. $\angle$BCD = $\angle$ADC and $\angle$ACB = $\angle$BDA. Prove that AD = BC and $\angle$A = $\angle$B.

                         
        $∆$ABC and $∆$ABD are two triangles on the same base AB, If line segment CD is bisected by 

Q22. AB at O. Show that ar (ABC ) = ar (ABD)
                       
          Express x = 3y in the form ax + by + c = 0 and indicate the value of a, b and c. Write two 
           solutions of the equation.