| Step | Hyp | Ref
 | Expression | 
| 1 |   | elex 2774 | 
. 2
⊢ (𝐴 ∈ 𝑉 → 𝐴 ∈ V) | 
| 2 |   | sbcexg 3044 | 
. . . 4
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥]∃𝑤(𝑤 = {𝑦 ∣ 𝜑} ∧ 𝑤 ∈ 𝐵) ↔ ∃𝑤[𝐴 / 𝑥](𝑤 = {𝑦 ∣ 𝜑} ∧ 𝑤 ∈ 𝐵))) | 
| 3 |   | sbcang 3033 | 
. . . . . 6
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥](𝑤 = {𝑦 ∣ 𝜑} ∧ 𝑤 ∈ 𝐵) ↔ ([𝐴 / 𝑥]𝑤 = {𝑦 ∣ 𝜑} ∧ [𝐴 / 𝑥]𝑤 ∈ 𝐵))) | 
| 4 |   | sbcalg 3042 | 
. . . . . . . . 9
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥]∀𝑦(𝑦 ∈ 𝑤 ↔ 𝜑) ↔ ∀𝑦[𝐴 / 𝑥](𝑦 ∈ 𝑤 ↔ 𝜑))) | 
| 5 |   | sbcbig 3036 | 
. . . . . . . . . . 11
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥](𝑦 ∈ 𝑤 ↔ 𝜑) ↔ ([𝐴 / 𝑥]𝑦 ∈ 𝑤 ↔ [𝐴 / 𝑥]𝜑))) | 
| 6 |   | sbcg 3059 | 
. . . . . . . . . . . 12
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥]𝑦 ∈ 𝑤 ↔ 𝑦 ∈ 𝑤)) | 
| 7 | 6 | bibi1d 233 | 
. . . . . . . . . . 11
⊢ (𝐴 ∈ V → (([𝐴 / 𝑥]𝑦 ∈ 𝑤 ↔ [𝐴 / 𝑥]𝜑) ↔ (𝑦 ∈ 𝑤 ↔ [𝐴 / 𝑥]𝜑))) | 
| 8 | 5, 7 | bitrd 188 | 
. . . . . . . . . 10
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥](𝑦 ∈ 𝑤 ↔ 𝜑) ↔ (𝑦 ∈ 𝑤 ↔ [𝐴 / 𝑥]𝜑))) | 
| 9 | 8 | albidv 1838 | 
. . . . . . . . 9
⊢ (𝐴 ∈ V → (∀𝑦[𝐴 / 𝑥](𝑦 ∈ 𝑤 ↔ 𝜑) ↔ ∀𝑦(𝑦 ∈ 𝑤 ↔ [𝐴 / 𝑥]𝜑))) | 
| 10 | 4, 9 | bitrd 188 | 
. . . . . . . 8
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥]∀𝑦(𝑦 ∈ 𝑤 ↔ 𝜑) ↔ ∀𝑦(𝑦 ∈ 𝑤 ↔ [𝐴 / 𝑥]𝜑))) | 
| 11 |   | abeq2 2305 | 
. . . . . . . . 9
⊢ (𝑤 = {𝑦 ∣ 𝜑} ↔ ∀𝑦(𝑦 ∈ 𝑤 ↔ 𝜑)) | 
| 12 | 11 | sbcbii 3049 | 
. . . . . . . 8
⊢
([𝐴 / 𝑥]𝑤 = {𝑦 ∣ 𝜑} ↔ [𝐴 / 𝑥]∀𝑦(𝑦 ∈ 𝑤 ↔ 𝜑)) | 
| 13 |   | abeq2 2305 | 
. . . . . . . 8
⊢ (𝑤 = {𝑦 ∣ [𝐴 / 𝑥]𝜑} ↔ ∀𝑦(𝑦 ∈ 𝑤 ↔ [𝐴 / 𝑥]𝜑)) | 
| 14 | 10, 12, 13 | 3bitr4g 223 | 
. . . . . . 7
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥]𝑤 = {𝑦 ∣ 𝜑} ↔ 𝑤 = {𝑦 ∣ [𝐴 / 𝑥]𝜑})) | 
| 15 |   | sbcabel.1 | 
. . . . . . . . 9
⊢
Ⅎ𝑥𝐵 | 
| 16 | 15 | nfcri 2333 | 
. . . . . . . 8
⊢
Ⅎ𝑥 𝑤 ∈ 𝐵 | 
| 17 | 16 | sbcgf 3057 | 
. . . . . . 7
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥]𝑤 ∈ 𝐵 ↔ 𝑤 ∈ 𝐵)) | 
| 18 | 14, 17 | anbi12d 473 | 
. . . . . 6
⊢ (𝐴 ∈ V → (([𝐴 / 𝑥]𝑤 = {𝑦 ∣ 𝜑} ∧ [𝐴 / 𝑥]𝑤 ∈ 𝐵) ↔ (𝑤 = {𝑦 ∣ [𝐴 / 𝑥]𝜑} ∧ 𝑤 ∈ 𝐵))) | 
| 19 | 3, 18 | bitrd 188 | 
. . . . 5
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥](𝑤 = {𝑦 ∣ 𝜑} ∧ 𝑤 ∈ 𝐵) ↔ (𝑤 = {𝑦 ∣ [𝐴 / 𝑥]𝜑} ∧ 𝑤 ∈ 𝐵))) | 
| 20 | 19 | exbidv 1839 | 
. . . 4
⊢ (𝐴 ∈ V → (∃𝑤[𝐴 / 𝑥](𝑤 = {𝑦 ∣ 𝜑} ∧ 𝑤 ∈ 𝐵) ↔ ∃𝑤(𝑤 = {𝑦 ∣ [𝐴 / 𝑥]𝜑} ∧ 𝑤 ∈ 𝐵))) | 
| 21 | 2, 20 | bitrd 188 | 
. . 3
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥]∃𝑤(𝑤 = {𝑦 ∣ 𝜑} ∧ 𝑤 ∈ 𝐵) ↔ ∃𝑤(𝑤 = {𝑦 ∣ [𝐴 / 𝑥]𝜑} ∧ 𝑤 ∈ 𝐵))) | 
| 22 |   | df-clel 2192 | 
. . . 4
⊢ ({𝑦 ∣ 𝜑} ∈ 𝐵 ↔ ∃𝑤(𝑤 = {𝑦 ∣ 𝜑} ∧ 𝑤 ∈ 𝐵)) | 
| 23 | 22 | sbcbii 3049 | 
. . 3
⊢
([𝐴 / 𝑥]{𝑦 ∣ 𝜑} ∈ 𝐵 ↔ [𝐴 / 𝑥]∃𝑤(𝑤 = {𝑦 ∣ 𝜑} ∧ 𝑤 ∈ 𝐵)) | 
| 24 |   | df-clel 2192 | 
. . 3
⊢ ({𝑦 ∣ [𝐴 / 𝑥]𝜑} ∈ 𝐵 ↔ ∃𝑤(𝑤 = {𝑦 ∣ [𝐴 / 𝑥]𝜑} ∧ 𝑤 ∈ 𝐵)) | 
| 25 | 21, 23, 24 | 3bitr4g 223 | 
. 2
⊢ (𝐴 ∈ V → ([𝐴 / 𝑥]{𝑦 ∣ 𝜑} ∈ 𝐵 ↔ {𝑦 ∣ [𝐴 / 𝑥]𝜑} ∈ 𝐵)) | 
| 26 | 1, 25 | syl 14 | 
1
⊢ (𝐴 ∈ 𝑉 → ([𝐴 / 𝑥]{𝑦 ∣ 𝜑} ∈ 𝐵 ↔ {𝑦 ∣ [𝐴 / 𝑥]𝜑} ∈ 𝐵)) |