theorem eqmaddd (G: wff) (a b c d n: nat):
  $ G -> mod(n): a = b $ >
  $ G -> mod(n): c = d $ >
  $ G -> mod(n): a + c = b + d $;
    
      
        | Step | Hyp | Ref | Expression | 
        
          | 1 | 
           | 
          eqmtr | 
          mod(n): a + c = b + c -> mod(n): b + c = b + d -> mod(n): a + c = b + d  | 
        
        
          | 2 | 
           | 
          hyp h1 | 
          G -> mod(n): a = b  | 
        
        
          | 3 | 
          2 | 
          eqmadd1d | 
          G -> mod(n): a + c = b + c  | 
        
        
          | 4 | 
           | 
          hyp h2 | 
          G -> mod(n): c = d  | 
        
        
          | 5 | 
          4 | 
          eqmadd2d | 
          G -> mod(n): b + c = b + d  | 
        
        
          | 6 | 
          1, 3, 5 | 
          sylc | 
          G -> mod(n): a + c = b + d  | 
        
      
    
    Axiom use
    axs_prop_calc
     (ax_1,
      ax_2,
      ax_3,
      ax_mp,
      itru),
    
axs_pred_calc
     (ax_gen,
      ax_4,
      ax_5,
      ax_6,
      ax_7,
      ax_10,
      ax_11,
      ax_12),
    
axs_set
     (elab,
      ax_8),
    
axs_the
     (theid,
      the0),
    
axs_peano
     (peano1,
      peano2,
      peano5,
      addeq,
      muleq,
      add0,
      addS,
      mul0,
      mulS)