| Step | Hyp | Ref | Expression | 
						
							| 1 |  | nfv | ⊢ Ⅎ 𝑥 ( 𝐴  ⊆  𝐵  ∧  𝐶  ⊆  𝐷 ) | 
						
							| 2 |  | nfra1 | ⊢ Ⅎ 𝑥 ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐷 𝜑 | 
						
							| 3 |  | ssralv | ⊢ ( 𝐴  ⊆  𝐵  →  ( ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐷 𝜑  →  ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐷 𝜑 ) ) | 
						
							| 4 | 3 | adantr | ⊢ ( ( 𝐴  ⊆  𝐵  ∧  𝐶  ⊆  𝐷 )  →  ( ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐷 𝜑  →  ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐷 𝜑 ) ) | 
						
							| 5 |  | df-ral | ⊢ ( ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐷 𝜑  ↔  ∀ 𝑥 ( 𝑥  ∈  𝐴  →  ∀ 𝑦  ∈  𝐷 𝜑 ) ) | 
						
							| 6 | 4 5 | imbitrdi | ⊢ ( ( 𝐴  ⊆  𝐵  ∧  𝐶  ⊆  𝐷 )  →  ( ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐷 𝜑  →  ∀ 𝑥 ( 𝑥  ∈  𝐴  →  ∀ 𝑦  ∈  𝐷 𝜑 ) ) ) | 
						
							| 7 |  | sp | ⊢ ( ∀ 𝑥 ( 𝑥  ∈  𝐴  →  ∀ 𝑦  ∈  𝐷 𝜑 )  →  ( 𝑥  ∈  𝐴  →  ∀ 𝑦  ∈  𝐷 𝜑 ) ) | 
						
							| 8 | 6 7 | syl6 | ⊢ ( ( 𝐴  ⊆  𝐵  ∧  𝐶  ⊆  𝐷 )  →  ( ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐷 𝜑  →  ( 𝑥  ∈  𝐴  →  ∀ 𝑦  ∈  𝐷 𝜑 ) ) ) | 
						
							| 9 |  | ssralv | ⊢ ( 𝐶  ⊆  𝐷  →  ( ∀ 𝑦  ∈  𝐷 𝜑  →  ∀ 𝑦  ∈  𝐶 𝜑 ) ) | 
						
							| 10 | 9 | adantl | ⊢ ( ( 𝐴  ⊆  𝐵  ∧  𝐶  ⊆  𝐷 )  →  ( ∀ 𝑦  ∈  𝐷 𝜑  →  ∀ 𝑦  ∈  𝐶 𝜑 ) ) | 
						
							| 11 | 8 10 | syl6d | ⊢ ( ( 𝐴  ⊆  𝐵  ∧  𝐶  ⊆  𝐷 )  →  ( ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐷 𝜑  →  ( 𝑥  ∈  𝐴  →  ∀ 𝑦  ∈  𝐶 𝜑 ) ) ) | 
						
							| 12 | 1 2 11 | ralrimd | ⊢ ( ( 𝐴  ⊆  𝐵  ∧  𝐶  ⊆  𝐷 )  →  ( ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐷 𝜑  →  ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐶 𝜑 ) ) |