Объяснение:
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парал. АBCD ∠А:∠В=4:5
∠А:∠В=4:5 ∠А=4х
∠А-? ∠В=5х
∠В-? ∠А+∠В=180°(по свойст. парал.)
4х+5х=180
9х=180
х=20°
∠А=4х=80°
∠В=5х=100°
∠А=∠С; ∠В=∠Д (по свойст парал)