| Step | Hyp | Ref | Expression | 
						
							| 1 |  | elreal |  |-  ( A e. RR <-> E. x e. R. <. x , 0R >. = A ) | 
						
							| 2 |  | elreal |  |-  ( B e. RR <-> E. y e. R. <. y , 0R >. = B ) | 
						
							| 3 |  | elreal |  |-  ( C e. RR <-> E. z e. R. <. z , 0R >. = C ) | 
						
							| 4 |  | breq1 |  |-  ( <. x , 0R >. = A -> ( <. x , 0R >. . <-> A . ) ) | 
						
							| 5 |  | oveq2 |  |-  ( <. x , 0R >. = A -> ( <. z , 0R >. + <. x , 0R >. ) = ( <. z , 0R >. + A ) ) | 
						
							| 6 | 5 | breq1d |  |-  ( <. x , 0R >. = A -> ( ( <. z , 0R >. + <. x , 0R >. ) . + <. y , 0R >. ) <-> ( <. z , 0R >. + A ) . + <. y , 0R >. ) ) ) | 
						
							| 7 | 4 6 | bibi12d |  |-  ( <. x , 0R >. = A -> ( ( <. x , 0R >. . <-> ( <. z , 0R >. + <. x , 0R >. ) . + <. y , 0R >. ) ) <-> ( A . <-> ( <. z , 0R >. + A ) . + <. y , 0R >. ) ) ) ) | 
						
							| 8 |  | breq2 |  |-  ( <. y , 0R >. = B -> ( A . <-> A  | 
						
							| 9 |  | oveq2 |  |-  ( <. y , 0R >. = B -> ( <. z , 0R >. + <. y , 0R >. ) = ( <. z , 0R >. + B ) ) | 
						
							| 10 | 9 | breq2d |  |-  ( <. y , 0R >. = B -> ( ( <. z , 0R >. + A ) . + <. y , 0R >. ) <-> ( <. z , 0R >. + A ) . + B ) ) ) | 
						
							| 11 | 8 10 | bibi12d |  |-  ( <. y , 0R >. = B -> ( ( A . <-> ( <. z , 0R >. + A ) . + <. y , 0R >. ) ) <-> ( A  ( <. z , 0R >. + A ) . + B ) ) ) ) | 
						
							| 12 |  | oveq1 |  |-  ( <. z , 0R >. = C -> ( <. z , 0R >. + A ) = ( C + A ) ) | 
						
							| 13 |  | oveq1 |  |-  ( <. z , 0R >. = C -> ( <. z , 0R >. + B ) = ( C + B ) ) | 
						
							| 14 | 12 13 | breq12d |  |-  ( <. z , 0R >. = C -> ( ( <. z , 0R >. + A ) . + B ) <-> ( C + A )  | 
						
							| 15 | 14 | bibi2d |  |-  ( <. z , 0R >. = C -> ( ( A  ( <. z , 0R >. + A ) . + B ) ) <-> ( A  ( C + A )  | 
						
							| 16 |  | ltasr |  |-  ( z e. R. -> ( x  ( z +R x )  | 
						
							| 17 | 16 | adantr |  |-  ( ( z e. R. /\ ( x e. R. /\ y e. R. ) ) -> ( x  ( z +R x )  | 
						
							| 18 |  | ltresr |  |-  ( <. x , 0R >. . <-> x  | 
						
							| 19 | 18 | a1i |  |-  ( ( z e. R. /\ ( x e. R. /\ y e. R. ) ) -> ( <. x , 0R >. . <-> x  | 
						
							| 20 |  | addresr |  |-  ( ( z e. R. /\ x e. R. ) -> ( <. z , 0R >. + <. x , 0R >. ) = <. ( z +R x ) , 0R >. ) | 
						
							| 21 |  | addresr |  |-  ( ( z e. R. /\ y e. R. ) -> ( <. z , 0R >. + <. y , 0R >. ) = <. ( z +R y ) , 0R >. ) | 
						
							| 22 | 20 21 | breqan12d |  |-  ( ( ( z e. R. /\ x e. R. ) /\ ( z e. R. /\ y e. R. ) ) -> ( ( <. z , 0R >. + <. x , 0R >. ) . + <. y , 0R >. ) <-> <. ( z +R x ) , 0R >. . ) ) | 
						
							| 23 | 22 | anandis |  |-  ( ( z e. R. /\ ( x e. R. /\ y e. R. ) ) -> ( ( <. z , 0R >. + <. x , 0R >. ) . + <. y , 0R >. ) <-> <. ( z +R x ) , 0R >. . ) ) | 
						
							| 24 |  | ltresr |  |-  ( <. ( z +R x ) , 0R >. . <-> ( z +R x )  | 
						
							| 25 | 23 24 | bitrdi |  |-  ( ( z e. R. /\ ( x e. R. /\ y e. R. ) ) -> ( ( <. z , 0R >. + <. x , 0R >. ) . + <. y , 0R >. ) <-> ( z +R x )  | 
						
							| 26 | 17 19 25 | 3bitr4d |  |-  ( ( z e. R. /\ ( x e. R. /\ y e. R. ) ) -> ( <. x , 0R >. . <-> ( <. z , 0R >. + <. x , 0R >. ) . + <. y , 0R >. ) ) ) | 
						
							| 27 | 26 | ancoms |  |-  ( ( ( x e. R. /\ y e. R. ) /\ z e. R. ) -> ( <. x , 0R >. . <-> ( <. z , 0R >. + <. x , 0R >. ) . + <. y , 0R >. ) ) ) | 
						
							| 28 | 27 | 3impa |  |-  ( ( x e. R. /\ y e. R. /\ z e. R. ) -> ( <. x , 0R >. . <-> ( <. z , 0R >. + <. x , 0R >. ) . + <. y , 0R >. ) ) ) | 
						
							| 29 | 1 2 3 7 11 15 28 | 3gencl |  |-  ( ( A e. RR /\ B e. RR /\ C e. RR ) -> ( A  ( C + A )  | 
						
							| 30 | 29 | biimpd |  |-  ( ( A e. RR /\ B e. RR /\ C e. RR ) -> ( A  ( C + A )  |