In the figure, ∠POR  and ∠ QOR form a linear pair. If a – b = 80°, find the values of a and b.
             

∠ POR and ∠ QOR form a linear pair. (given)
.^.. ∠a + ∠b  = 180°      (Two adjacent angles form a linear if and only if they are 
                               supplementary) --------------- (1) 
   ∠a - ∠b =  80°                        ------------------- (2)
Adding (1) and (2)
   2∠a = 180^o +80° = 260^o
   ∠a = 130°
Substituting ∠a = 130° in (1) 
    130° + ∠b = 180°
.^..  ∠b = 180° - 130° = 50°.